Sorry mate bit crap info, however, from the HSE.
Assume that roofs are fragile unless you can confirm otherwise - there may be non-visible damage caused by weathering, deterioration, etc.
Always avoid working on a roof if it is possible to carry out the work in another way, eg approaching the roof from below.
Never go onto any part of a fragile roof without using platforms to support your weight.
Fit appropriate warning signs to buildings which have fragile roofs, particularly at roof access points.
Never walk along the line of the purling bolts - it is like walking a tightrope.
Ensure that platforms are wide enough and long enough to give adequate support across roof members and ensure that enough platforms are provided on the roof.
Protect against falling through the fragile roof adjacent to the platform by providing:
a properly installed safety net, scaffolding or similar close to the underside of the roof; or
suitable guard rails and toe boards at the edges of the platform; or
further suitable coverings over all fragile materials within 2m of the working platform.
---------- Post added at 02:30 PM ---------- Previous post was at 02:25 PM ----------
The hierarchy of controls for WAHR 2005, is the Kidda mate, then hopefully the situation can be resolved at the upper levels.