Well it may have been revenge. The issue occurred because I complained to my insurance company that my roof had been damaged when my neighbours rental house was re roofed. It was the same roofer and I could tell there was bad feeling.
I unfortunately had a dodgy roofer working on my slate roof. The work he did was appalling cracking slates etc. I don't think that he supported his weight while working. Anyway my biggest fear is that he may have deliberately damaged my roof. Someone said that he could have removed the nails...