Leaks behind a parapet, found months late
The Georgian and Victorian roofs in SE1 are shallow and sit behind a parapet wall, so the owner cannot see the roof from the street or from any window. There is no moment where somebody notices a slipped slate. The first sign of failure is a stain on a ceiling in the flat below, by which time water has been sitting in the build-up for weeks. On these buildings a scheduled inspection is not a luxury, it is the only way the roof gets looked at at all.