For many decades we had the National Anthem at the end of a film in the cinema, but I don't recall anyone actually singing along. Similarly in theatres etc. It was played, but it was not expected that one sang. As a Brownie and Girl Guide, we learned verses one and two (Thy choicest gifts in store etc) It's only fairly recently that sportsmen/women have been 'expected' to sing the words.
I go along with Billy Connelly; the Archers tune is far jollier.