In message ,
lesshaste writes
In one of the rooms in my house I have found that one of the two
electrical wall sockets in the pair does not appear to work at all.
Sorry to ask such a beginner's question but what is the best way to
diagnose/fix the problem?

Do you mean one of the two sockets in a double socket outlet? If so then
best thing to do is just replace it
--
Chris French, Leeds