Dave A wrote:

I checked the other applicances in the kitchen and found them to all
have the same reading - I eventually traced this to a faulty socket
which I have replaced and all seems ok.

Good. For the satisfaction of my curiousity (and those of others
following the thread, I expect) - what was the fault in the socket? Was
it some rare, generally-unlikely internal fault which meant that the
incoming earth wires were well attached to the E terminal in the socket,
but the connection wasn't being made to the plug's E pin?

Or was it something much simpler - loose or simply missing connection to
the E terminal of the socket, or maybe incoming E fixed not to socket
but to the terminal in the back box (which if the socket's plastic,
gives you no earth connection to the socket itself)?

Enquiring minds wanna know... and are glad you're no longer getting
shocks, by the way.