Tomorrow’s World, the long-running BBC technology programme, has put some of its film archive online, including one about the first home computer terminal in Europe, broadcast in 1967.

On Breakfast this morning, they played a clip of a Tomorrow’s World April Fool, where the presenter climbed into a dustbin and blew himself up. It wasn’t very impressive but it reminded my Grandad of a hoax he spotted on TV years ago when he was a teacher.

The BBC were reporting on a crucial international chess match taking place in London. Grandmasters had come from all over the world to congregate round a chess board in the middle of Trafalgar Square.

As the players stood about, talking seriously in their various native tongues, Grandad realised the young men on screen were actually his pupils from Hackney Downs in east London. And rather than discussing the match going on in front of them, they weren’t actually talking about chess at all, they were just pretending to be fluent in German by reciting extracts from Goethe’s Faust, which their German teacher, my Grandad, had got them to learn off by heart.

I bet there’s no footage left in the BBC archive – but it’s a shame Grandad told me the story two days after I left the BBC, so I can no longer look on the intranet to check.