just been called out to a fault. lighting circuit tripping RCD, but only when MCB is closed, so a L-E, i suspect. tenant has just moved in and has had a look at 1 fitting, seen the state of it , then called me. found cables in landing light crumbling insulation, although pvc. same in kitchen light. bare conductors all over the place. no visible main earth. water bond disconnected and just lying there. recent niceic CU change, looks like a monkey's nest. CU jammed hard against DNO board so needs a crowbar to refit the cover. 10mm shower circuit run externally in unprotected T/E. issuing a danger notice.