In article ,
Hamish wrote:
All the wiring in my new house is run in conduit which acts as the earth.

The conduit terminates in metal boxes approx 5"x"2.5" with the 15 amp
faceplate fixed by four screws in the corners.

Is it possible to buy adaptor plates for these old style boxes or do I
have to replace them and ,if so, how should the earth connection be
secured.

Also, is it permissible to run earth connections from the terminals in
new boxes to existing conduit runs fixed by an earthing strap?

I'm surprised you don't want extra sockets, or to re-locate the existing
ones.

IMHO, ignore the conduit as an earth, and run earth wires through it where
it's in suitable places to be re-used.

Remove the old boxes and replace with modern ones. What conduit you end up
re-using will then simply be a convenient and well protected run for
modern cable, but with no electrical function.. It might well save some
time for lighting switch drops.

--
*In "Casablanca", Humphrey Bogart never said "Play it again, Sam" *

Dave Plowman London SW 12
RIP Acorn