I once came across this in a DIY job completely accidently:
Shower was installed as per normal EXCEPT:
a cable came from the ceiling into the side of the shower via a gland. It was nicely looped down in the shower tray.
I removed the fuse for the shower and kept the carrier & not only called the landlord to give him an ear full but also the local athority's building inspectors and told the tenants to contact the citizens advice bureau and under no circumstances to use the shower.
The house had no RCD for the sockets or the shower which is illegal in rental accomodation. Although given the ridiculous rental market at the lower end of the scale people will take anything due to lack of supply.
