Yes, I remember it being when Jo and Three were having a trip to Peladon. I clearly just don't remember any actual plot. ;-)

Well, I suppose everything happens somewhere down some leg of the trousers of time, but I couldn't possibly comment.

But, you know, he was the voice on the radio, so maybe? Doesn't that get followed up on in Blood Heat? (Yes, another book I ... well, I think that one did at least get sold at a car boot, or something, so I got some pennies back.)