Whilst clearing out our loft I have noticed a damp patch at the apex of one of the roof trusses. It looks as if there could be a minor leak in the roofing felt but I can't see any gaps through it when I look with a torch.
Can anyone hazard a guess at the likely problem ? For context the roof construction is trussed rafters - early 1980's construction. I've attached a few photos of it.
My best guess was that a ridge tile might be loose - however from outside nothing seems to be seriously out of place.
I'm concerned of possible structural problems with the roof if I don't get this sorted quickly.
Any ideas about what might be wrong or the best first step in finding out would be greatly appreciated