I think audiences in those days were much more restrained Robert, and applause when a singer started a song, even a well known favourite, was not considered acceptable in the UK.
It is only in recent years we have followed the Americans lead for this to be accepted here, and become a regular occurrence at UK concerts and shows.
I used to think it would put the singer off, but it doesn't appear to.
Imagine if it happened at a Classical concert though!!!!!!!
Marian