Round this way many council properties built in the 50s have metal door frames with architrave switches cut into them. The conduit enters at the top and single core cables drop down to the switch. No back box. Although i have seen this many times i recently had to do a PIR & 'failed' it only as it was not earthed. I commented about the containment issue only as the frames are all steel & i suppose a big switch box ( IMHO not really correct)
