when digital channels slide off air

TV It's quite comforting to know that when digital channels slide off air as BBC Parliament did last night at around midnight, that the only recourse for filling in is some text created on a BBC Micro superimposed over the shot from an analogue camera plonked on top of (I think) television centre.

It's like one of those nightmarish messages for Alex Drake in Ashes to Ashes. If you watched for long enough, a tube train passed through somewhere in the foreground.