Thanks for your offer of help.

My son sorted out the problem. I had modified the example page ‘Coming Soon’ and – being very new to WordPress, had marked all the other pages private. Apparently, this left the page as a ‘child’ with no valid ‘parent’. That means nothing to me but might make sense to you…! He said I was also having problems with a plugin called ‘Redirect’ which was incorrectly configured and redirecting the home page back to itself in a sort of loop.

I hope this will prove useful in helping people with similar problems in the future.