Last year, I think, one of the shows mentioned that ITT was broadcast live, and it did not come from Television Centre.
The ITT studio was in a separate part of London. I guessed there was some sort of outside broadcast link, sending the signal, perhaps from a van, or a rooftop dish, back to Television Centre.
I thought that maybe a passing plane, or some such thing, was briefly interfering with the signal.
But it's only a guess, and I don't really know.