Ah ! Moronic little box thought it was a "duplicate".
No, I don't know either.
Thanks for the heads up, but once the moment has passed (I was looking forward to watching it delayed by 10-15 minutes) then the TiVo is just a paperweight. I have 4 other ways to get iPlayer, none of which involves a TiVo.
It's usefulness is declining daily.
The annoying thing is I checked before that it was definitely set to record (you can tell I'm an experienced TiVo user) and it said it was. So when was the earth-shattering (and incorrect) decision that it was a duplicate was made ?