AS THE ORIGINAL POSTER OF THIS THREAD, may I say thank you to Raimey, Drew and Stephen Howell who passed on some very useful information answering my original question.

As to the other people who then decided to exercise their keyboard, perhaps I can ask them to now ignore this topic and go somewhere else. I have had over 30 e-mails alerting me to posts which are of no use or interest to me.

Historic Bore