This is John Peel playing Fripp and Eno’s album backwards on BBC Radio One on 18th December 1973, without anyone in the studio knowing any difference. The story goes that Brian Eno was driving in his car, listening to Peel’s show, and he had the shock of his life when he heard Peel was playing his album backwards. He tried to phone the BBC to let Peel know that, but the BBC engineers thought it was an imposter playing a prank, therefore putting the phone down on him. Peel told his listeners at the end that it was an album worth buying, without realising he was playing it backwards!
P.S. Try playing this and the adjacent Japanese court music post simultaneously!