ROOF ANCHOR CABLE SYSTEM HAVING SHOCK ABSORBING MEANS This application is a divisional of application Nos.. AU 2009210368 and AU 2009266424, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD 5 The present invention relates to a roof anchor for attaching devices, apparatus or equipment to a roof surface and, more particularly, to a roof anchor cable system, which includes shock absorbing means, for fixing about a rafter or the like of a roof structure supporting tiles so that the attachment point of the anchor is available for use on the roof surface. The devices, apparatus or equipment to be attached may include safety equipment such as a safety harnesses, 0 ropes or other safety devices adapted to secure a roof worker against falling and injury. BACKGROUND ART The following references to and descriptions of prior proposals or products are not intended to be, and are not to be construed as, statements or admissions of common general knowledge in the art. In particular, the following prior art discussion does not relate to what is commonly or 5 well known by the person skilled in the art, but assists in the understanding of the inventive step of the present invention of which the identification of pertinent prior art proposals is but one part. Several solutions have been proposed for providing anchor points on a roof, whereby such anchor points are made available so that a person working on the roof for example, can attach 20 himself to the anchor point by means of a rope or cable etc, so that in the event of a fall, he will be constrained from falling off the roof. Various solutions have been put forward which are particularly suitable for metal rooves, both for initial installation when the roof covering is first applied and in cases where the roof covering is already attached, being a so-called retro- fit. None of these solutions, however, is really practical when one considers a tiled roof. Generally 25 because of the ease of removing one or two or even more tiles, the problems associated with so called retro-fits for metal sheeting rooves are less apparent. To this end, a solution which 1 provides an anchor point in a tiled roof, if suitably designed, should in general be applicable not only to tiled rooves when they are being constructed, but also when the roof tiles are already in place, since the tiles can generally be easily removed and replaced without too much difficulty. 5 However, unlike the possibilities available for metal rooves, where there is both integrity in the metal roof itself, as well as the way in which the metal sheeting is itself attached, the anchor point for a tile roof needs to be preferably independent of the tiles themselves (that is to say preferably not made to pass through a tile as such, or otherwise rely on the arrangement of tiles) and yet available in such away that it so stands proud of the roof surface and yet does not 0 interfere with the actual arrangement of tiles. It would therefore be advantageous if a roof anchor system were available which could be affixed to the rafter of a roof structure supporting tiles, and which also provided an anchor point which extended beyond the surface of the roof tiles, without disturbing the usual arrangement of tiles. It would also be advantageous if such a roof 5 anchor system was provided with shock absorbing means in order to minimise injury from a person utilising the anchor point in the event of a fall. OBJECT OF THE INVENTION It is an object of the present invention to provide a roof anchor system which ameliorates one or more of the abovementioned disadvantages associated with the prior art, particularly by 20 providing a roof anchor system which may be mounted on the rafter of a roof structure supporting tiles, the anchor point for attachment of devices, apparatus or equipment, being made available above the roof surface, the anchor system so designed as to progressively absorb the effects of a sudden load applied thereto. It should also be understood that whilst the invention relates primarily to the attachment of 25 devices to a tiled roof as described, the invention will also be applicable in many instances where attachment of a device to another surface or structure is required, whether a wall or ceiling for example. Thus any reference to a roof is also meant to encompass reference to any structure, where, by suitable adaptation the invention may also be utilised. Similarly, although 2 the invention is described generally in terms of its applicability to tiled rooves, it is again to be understood that the invention is applicable to any roof covering, where, by suitable modification , the invention may also be applied. DISCLOSURE OF THE INVENTION 5 According to the present invention, there is provided a roof anchor bracket comprising: an outer leg comprising an eyelet for engagement to fall safety equipment; a first inner leg and a second inner leg, the first and second inner legs continuous with the outer leg, the second inner leg having a shock absorbing region that is formed in a snake-like pattern and an attachment bracket attachable by fasteners extending through apertures in the 0 attachment bracket to a roof structure , wherein the roof anchor bracket is bent along its length to form a generally flattened W-shape in profile. The roof anchor bracket may be bent along its length between the outer leg and the first inner leg, between the first inner leg and the second inner leg, and between the shock absorbing 5 region and the attachment bracket. The attachment bracket may lie in a different plane to the shock absorbing region. The first inner leg may comprise a flat strap and the second inner leg may comprise a serpentine portion. Preferably, the roof anchor bracket is die cut from a single sheet of material. 20 Preferably, there is a breakable connection extending between the shock absorbing region and the attachment bracket. The roof anchor bracket may form part of a roof anchor cable system for fitment to a rafter or the like of a roof structure, wherein the anchor cable system comprises a cable and an anchor bracket, wherein in use the cable is attachable about a rafter or the like by means of simply 25 wrapping the cable thereabouts, the free ends of the cable being connectable in use to the anchor bracket, the anchor bracket comprising first attachment means for attaching the free 3 ends of the cable thereto, second attachment means remote therefrom and able to extend through or beyond the roof cladding such as tiles or the like for attaching devices, apparatus or equipment to the anchor bracket, and third attachment means for attaching the anchor bracket itself to the rafter for the purpose of generally locating the bracket in the desired position. 5 Preferably the anchor bracket and cable cooperate to progressively distort under sudden load. To this end, the very nature of the cable wrapped about the rafter provides a significant contribution to the absorption of energy in cases where a person falls. It should be appreciated that the performance of this arrangement will be improved when the cable is wrapped along rather than simply around the rafter. 0 The performance of the cable in absorbing a sudden load applied thereto will be thus particularly enhanced where a timber rafter is utilised, the timber being inherently compressible to a degree, providing a significant shock absorbing capacity. However, even in the case of a metal roof truss, the action of having the cable wrapped about the rafter provides significant progressive absorption of the energy under sudden load, especially with increasing numbers of 5 crossovers as the cable is wrapped about a longer length of the rafter. To this extent, in the case of metal rafters, it is preferable to have the cable wrapped four times thereabouts (ie with three crossovers). In any event, preferably the cable is wrapped more than once around the rafter (ie not merely looped around the rafter once) and is preferably located initially by means of a simple bracket 20 conveniently located to affix it to the rafter. This bracket will be best located where the cable effectively loops the rafter. Conveniently, this bracket will be located on the upper side of the rafter (for ease of attachment) when one or an odd number of crossovers occurs, the bracket of course also be located on the upper side of the rafter. Generally speaking, this locating bracket for the cable will perform no useful function other than to keep the cable in place along the 25 rafter until a load should be applied, in which case the cable will then be caused to tighten about the rafter (biting into the wood thereof if made of timber), but otherwise performing in such a way that it will not move when under such load. 4 Preferably the anchor bracket itself is also shaped so as to progressively distort under sudden load. In addition to the natural shock absorption provided by the use of a cable wrapped about a rafter, it is highly desirable to also provide shock absorption means in the bracket itself. For example, this may take the form of one or more planar sections of the bracket, die-cut in a 5 generally snake like pattern, so that upon a force being applied thereto, the thus shaped section is able to extend progressively under the load applied. Preferably, the anchor bracket is thus die cut from a single sheet of stainless steel, aluminium or high density plastics material and cut so as to provide progressive absorption of a sudden load applied thereto by means of progressive deformation of the bracket under such load. 0 Preferably the shock absorption is thus provided by one or more suitably shaped portions of material cut or otherwise formed so that when a force is applied thereto, there is created a deformation therein in the form of a generally linear extension of that portion, ie by effectively straightening or "unbending" such region. Thus the anchor is so designed that deformation by bending, ie unbending or straightening, of such shock absorbing region provides an absorption 5 of the forces applied to the anchor. Whilst it is generally preferred that the anchor bracket be made from a generally planar section of material as described above, it is preferable that the bracket itself be bent in such a way that it can be both suitably attached to a rafter at one end, whilst having the other end remote therefrom extend between overlapping tiles. To this end, the cross section may be usefully 20 described as a generally flattened W profile, the outer legs corresponding to regions supporting in the one case the second attachment means for devices etc, ie standing proud of the tile surface, whilst in the other case, the other outer leg corresponds to a region supporting the third attachment means for affixing the bracket to the rafter. The intermediate legs therefore allow the bracket to function in so far as they connect both ends and allow the region supporting the 25 second attachment means to pass effectively between the tiles. Generally, it is preferred that the inner leg adjacent the outer leg which supports the third attachment means is the region supporting the first attachment means, ie for attaching the cable. It will be appreciated however that other cross sectional shapes other than a flattened W profile, may also be employed. 5 Preferably the first attachment means provided in the anchor bracket for fixing the cable thereto is in the form of a simple hole therethrough. Preferably the ends of the cable are provided with an end piece swaged thereto, in which there is also provided a hole. In this way, attachment of both ends of the cable to the anchor bracket is easily achieved by aligning the three holes and 5 passing a bolt etc to which a nut may be affixed, or other suitable fixing device therethrough for securement of the cable ends to the bracket by otherwise generally known means. The second means of attachment provided in the anchor bracket, ie for attaching the device, apparatus or equipment thereto, is again preferably provided in the form of a simple hole or eye in the end of the anchor which protrudes in use through the tile surface. 0 The third means of attachment provided in the anchor bracket is preferably in the form of a t section with a plurality of holes available therethrough for screwing the bracket to a rafter. In this way, although the main energy absorption of the bracket and cable combination is provided by the cable itself acting in conjunction with any absorption means provided in the bracket itself, the initial shock is absorbed in this arrangement by having the bracket also screwed to 5 the rafter as well as connected by the cable as described beforehand. More importantly however, the t-section allows location of the bracket at various cross wise positions on the rafter so that the other free end of the bracket, being that end which extends between adjacent overlapping tiles, may be properly located. In this way, the bracket may be conveniently located so that the free end extends between the tiles at a suitable point in their profile (eg 20 along a trough or groove etc) so that in essence , the tiles are not physically disturbed from the arrangement which they would normally assume if the anchor bracket were not there. It will be understood from the embodiments described herein, that the roof anchor cable system is also able to function irrespective of the direction of the load, notwithstanding that in doing so there will be some disturbance of the tiles about the free end of the anchor in the event of such 25 a load being applied in certain directions. BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood from the following non-limiting description of various embodiments of the present invention with reference to the drawings in which: 6 Figure 1 is a side view of a roof anchor cable system according to one embodiment of the invention, showing three overlaps in the cable about a rafter; Figure 2 is a side view of the roof anchor cable system as shown in Fig. 1 without the rafter; Figure 3 is a plan view of the roof anchor cable system as shown in Fig. 2; 5 Figure 4 is a side view of the roof anchor cable system according to the embodiment shown in Figs. 1 to 3, but showing instead a single overlap in the cable about a rafter; Figure 5 is a side view of the roof anchor cable system as shown in Fig. 4 without the rafter; Figure 6 is a plan view of the roof anchor cable system shown in Fig. 5; Figure 7 is a side view of the roof anchor cable system according to the embodiment shown in 0 Figs. 1 to 6, but showing a double overlap in the cable about a rafter; Figure 8 is a detailed plan view of the anchor bracket as used in the embodiments of s Figs. 1 to 7; Figures 9 to 12a are plan views of other embodiments of the anchor bracket suitable for use with any of arrangements as shown in Figs. 1 to 7, substituting the bracket for the one shown as 5 appropriate; Figure 12b is a side view of the bracket shown in any one of Figs 8 - 12a; Figure 13 (Fig. 1 in AU 2009266424) is a perspective view of a roof anchor bracket showing a shock absorbing portion suitable for use in the embodiments of the bracket shown in Figs. 8 12a; 20 Figure 14 (Fig. 2 in AU 2009266424) is a plan view of a roof anchor bracket similar to that shown in Fig. 13, but with the bridge 15 lying in the same plane as the shock absorbing portion 14; Figure 15 (Fig. 3 in AU 2009266424) is a plan view of a roof anchor bracket showing a shock absorbing portion suitable for use in the embodiments of the bracket shown in Figs. 8 - 12a; 25 and 7 Figure 16 (Fig. 4 in AU 2009266424) is a plan view of a roof anchor bracket showing a shock absorbing portion suitable for use in the embodiments of the bracket shown in Figs. 8 - 12a. DETAILED DESCRIPTION OF THE DRAWINGS Referring generally to Figs 1 to 3, there is shown a roof anchor cable system generally 5 referenced 11 according to a first embodiment of the invention. The roof anchor cable system 11 comprises an anchor bracket 12 and a cable 13 for attachment to a rafter 14. The anchor bracket 12 in side view or in profile, is of generally flattened W shaped is configuration having a first outer leg 15 which is generally t-shaped, for attachment to the rafter 14, by known means such as screws (not shown). These may be inserted through holes 16 0 located in the first outer leg 15. The other outer leg 17 extends beyond the roof cladding, eg passing between consecutive tiles 18. The outer leg 17 has a hole 19 therethrough for attachment of devices, such as safety harnesses, ropes or other safety devices (not shown). The two inner legs 20, 21 are shaped or angled so as to allow the anchor bracket 12 to be affixed to the rafter 14 and extend between 5 consecutive tiles 17 as shown. The location of the several holes 16, in this case three, across the first outer leg 15, provides for location of the bracket 12 on the rafter 14, so that it can be aligned with any useful groove or trough etc in the profile of the tile (not illustrated), to minimise any disturbance thereto. Alternatively the anchor bracket of Fig. 9 may be employed wherein the bracket 12 has a wider 20 leg member 15 having five holes 16 located therein. Inner leg 1 has a hole 22 therethrough. The cable 12 is wrapped four times about the rafter 14, as illustrated in Fig 1, producing three overlaps 23. To this extent the cable 13 is wound twice about the rafter 14 moving upwards and away from the anchor bracket 12, and then wrapped a further two times coming back down the rafter to return to the anchor bracket 12. The two free 25 ends of the cable 13 are provided with end pieces 24 swaged thereto. Each end piece 24 has a hole 25 therethrough for fixing to the anchor bracket 12, by means of a nut and bolt 26 as shown, which passes through the holes 22 and 25 when aligned for that purpose. 8 Where the cable 13 passes over the rafter 14 before returning to the anchor bracket 12, it is secured by a holding bracket 27. This bracket 27 has a hole 28 therein for fixing to the rafter 14 by suitable means, such as a screw (not shown). Although the anchor bracket 12 as shown in Figs 1 to 3 has no regions therein acting as a shock 5 absorber, anchor brackets 12 incorporating shock absorbing regions as discussed below in relation to Figs 10 to 12a may be substituted instead. In any event, the use of the cable 13, wrapped up to four times around the rafter 14, provides excellent shock absorbing means in situations where a sudden load is applied to the anchor/cable combination 11. This arrangement is particularly suited to steel rafters. When a 0 force is applied to the anchor/cable system 11, the initial force causes the anchor bracket 1 to be separated from the rafter as the screws holding the first leg 15 of the bracket 12 give way. It follows, that the forces are then applied to the cable 13 which tightens progressively about the rafter 14. No slippage occurs even on a metal rafter 14, as the cable 13 bites into itself at the crossover points 23. 5 Figs 4 to 6 and Fig 7, in which like components are referenced with the same reference numerals, effectively illustrate less cross over points 23, specifically two in Figs 4 to 6 and only one in Fig 7. Less crossover points 23 have been found to be suitable in cases where timber rafters 14 are employed, although three as illustrated in Fig 1 to 3, is generally preferred even for timber rafters. It should be noted that in the case of two crossovers, as shown in Fig 7, the 20 geometry is such that the holding bracket 27 is actually located on the underside of the rafter 14, which may be inconvenient to affix in situations where the roof has already been otherwise finished, eg. in a so-called retro fit. Referring specifically to Figs 10 to 12b, there are illustrated alternate brackets 12 which have one or more regions 29 die cut so as to provide shock absorption under sudden load. The 25 principles involved have been discussed at length in Applicant's copending Australian patent application 200890341, entitled "Roof anchor with shock absorping means", the subject matter of which is incorporated herein by reference, and was the basis for the corresponding complete Australian application, No. AU2009266424. 9 In particular, in the complete specification, AU2009266424, corresponding with AU200890341, the preferred embodiments shown in AU200890341 and AU2009266424 will be described with reference to the drawings contained in that specification and with reference to the reference numerals used with respect to those drawings, noting that where the same 5 references numerals are used in earlier drawings in this specification, they now relate to the features shown only in Figs. 13 - 16, unless expressly stated otherwise. In Figs. 13 - 16 (corresponding to Figs. 1 - 4 in AU200890341 and AU2009266424), there is shown one or more breakable joins or connections 16 between the first fixing 13 and second attachment regions 15, which are designed to prevent the anchor 11 from simply bending under 0 initial load, but fails at a pre-determined load, whereby the load is then essentially exerted on the absorbing section(s) progressively. In the vicinity of the region where each shock absorbing portion 14 becomes the bridge region 15, there are provided small spanning joins 16 extending between that part of the shock absorber 14 and the nearest point on the attachment portion 12, the purpose of which is to 5 provide break points so that the initial load applied to the anchor 11 should a fall be experienced, does not cause the shock absorbing regions 14 to come into play until a predetermined initial load has been experienced. In this way initial unwanted bending of the anchor 11 at a single point is avoided. Accordingly, the breakable connection 16 extends between the shock absorbing region 14 and the attachment portion 12. 20 Essentially, these shock absorbing regions 29, where provided in bracket 12, co-operate with the cable 13 to further enhance the shock absorbing capacity of the bracket cable system, so that when a sudden load is applied, for example as a result of a person attached to the anchor system falling, the initial and subsequent forces are absorbed to the extent that the person who falls is not injured by being suddenly prevented from falling had there been no shock 25 absorption provided. In the preferred embodiments shown in Figs. 9 - 12b, the roof anchor bracket 12 comprises: an outer leg 17 comprising an eyelet 19 for engagement to fall safety equipment; 10 a first inner leg 20 and a second inner leg 21, the first and second inner legs 20,21 continuous with the outer leg 17, the second inner leg having a shock absorbing region 29 (Fig. 12a) that is formed in a snake-like pattern and an attachment bracket 15 attachable by fasteners extending through apertures 16 (13 in AU2009266424) in the attachment bracket 15 to a roof structure 5 14. The roof anchor bracket 12 is bent along its length to form a generally flattened W shape in profile. The W-shaped profile contributes to the roof anchor bracket's 15 capacity to conform to the shape of layered roof tiles whilst enabling fixation to a roof structure under the tiles. In Fig. 10, the bracket 12 comprises a pair of serpentine or snake-like folded portions 29, 21 in the first inner leg 20 and the second inner leg 21, respectively. The serpentine portions o comprise bends in the length of the bracket 12 that bend one way, then another like pleated folds, whilst each serpentine portion 29,21 lies in its own flat first or second plane, respectively. In Fig. 11, the serpentine portion 29 is identical to that of the embodiment shown in Fig. 10, but the second inner leg is a flat strap 21. In each case, the second inner leg 21 comprises a hole 22 formed in a donut portion of the second inner leg 21, as described above. 5 In Fig. 12a, an outer leg 17 comprises an eyelet 19 lying in an outer plane adapted to receive or attach to safety equipment. The first inner leg comprises a flat strap 20 lying in a first plane inclined relative to the outer plane. The transition from the outer leg 17 to the first inner leg 20 comprises a bent section (each bend shown in Fig. 12b in the bracket 12 is designated by reference numeral 30) having an angle of about 110 - 170*, preferably 1350 - 155', and most 20 preferably about 145'. The first inner leg 20 transitions to a second inner leg 21 via a bend 30 having an angle of about 1100 - 170*, preferably 1350 - 1550, and most preferably about 1500. The second inner leg 21 includes a serpentine portion 29 having folds that bend one way and then another whilst the second outer leg 21 lies in a single second plane. The second inner leg 21 therefore lies in the second plane which is at an angle to the first plane and may be 25 substantially parallel to the outer plane. Further to Fig. 12a, an attachment portion 15 extends from the second outer leg 21 and lies in rafter plane that is inclined relative to the second plane at an angle generally determined by the incline of the rafter plane to which it is to be affixed in a specific application. Similarly, the 11 first plane is preferably determined by the angle of inclination of a roof line as the first inner leg is preferably sandwiched between upper and lower overlapping tiles (18 in Fig. 1). Accordingly, the angles of the bends between the bracket sections 20, 21, 15 are a function or strongly influenced by the roof pitch in any particular application. 5 In forming the shallow W-shaped profile shown clearly in Fig. 12b and in Fig. 1 in situ, the roof anchor brackets 12 are equipped to contribute to the way each bracket 12 functions to secure itself to a roof structure (the rafter 14 in Fig. 1) whilst presenting a suitable attachment means 19 for attachment to safety equipment. The W-shaped brackets 12 are bent along their length between the outer leg 17 and the first inner leg 20, between the first inner leg 20 and the 0 second inner leg 21, and between the shock absorbing region 29 and the attachment bracket 15. This enables the outer leg 17 bearing attachment means 19 to emerge from under and extend beyond a roof tile (18 in Fig. 1). It enables the first inner leg 20 to rest substantially in parallel with the underside surface of the roof tile. The W-shaped profile allows the second inner leg 21 to bridge the space between the underside of the roof tile and the rafter and the orientation of 5 the attachment portion 15 permits the attachment portion 15, integral with the rest of the roof anchor bracket 12, to be fastened to the rafter. The roof anchor bracket is die cut from a single sheet of material. The material may be sheet metal, such as steel, preferably galvanised or stainless steel. The attachment portion 15 lies in a different plane to the shock absorbing region 29 to 20 accommodate the requirement that the roof anchor comprise a W-shaped profile to provide an attachment means extending proud of the roof line (18 in Fig. 1) to the rafter spaced therefrom. It will appreciated that many modifications and variations may be made to the embodiments described herein by those skilled in the art without departing from the spirit or scope of the invention. 25 EXPLANATIONS OF TERMINOLOGY USED IN THE SPECIFICATION Throughout the specification and claims the word "comprise" and its derivatives are intended to have an inclusive rather than exclusive meaning unless the contrary is expressly stated or the context requires otherwise. That is, the word "comprise" and its derivatives will be taken to 12 indicate the inclusion of not only the listed components, steps or features that it directly references, but also other components, steps or features not specifically listed, unless the contrary is expressly stated or the context requires otherwise. In the present specification, terms such as "component", "apparatus", "means", "device" and 5 "member" may refer to singular or plural items and are terms intended to refer to a set of properties, functions or characteristics performed by one or more items having one or more parts. It is envisaged that where a "component", "apparatus", "means", "device" or "member" or similar term is described as being a unitary object, then a functionally equivalent object having multiple components is considered to fall within the scope of the term, and similarly, 0 where a "component", "apparatus", "assembly", "means", "device" or "member" is described as having multiple items, a functionally equivalent but unitary object is also considered to fall within the scope of the term, unless the contrary is expressly stated or the context requires otherwise. Orientational terms used in the specification and claims such as vertical, horizontal, top, 5 bottom, upper and lower are to be interpreted as relational and are based on the premise that the component, item, article, apparatus, device or instrument will usually be considered in a particular orientation, typically with the outer leg 17 uppermost. INDUSTRIAL APPLICABILITY It will be immediately apparent to persons skilled in the art that the roof anchor may provide an 20 anchor point for a variety of activities carried out on roof, including height safety, but not necessarily limited thereto. 13