custard and jelly; custard noun television; a television UK,1974 Rhyming slang for TELLY
[T]here’s nothing on the custard. — Ray Puxley, CockneyRabbit, 1992
It might even persuade “saucepan lids” (kids) to spend more time reading and less time in front of the “custard and jelly” (telly). — BBC News, 26 February 2001