I know this is off topic, but really this is the best newsgroup to ask on because you are all such clever people.
A friend who has a combi TV (TV with built in VHS) decided to record a programme off Ch4.
When he played it back, he got the video of Ch4 with the sound of ITV1.
I must admit, when he was telling me I was drinking a cup of tea at the time and, well you can guess the rest.
James