It's a simple premise: would the Tenth Doctor work in the Fourth Doctor's stories? Or vice versa? Could you reasonably swap the Third and First Doctors over? And just who could stand in for the Fifth?

Working it out (and perhaps wishing they hadn't started the conversation in the first place) are Christian Cawley and Gareth Kavanagh…

Shownotes

Day of the Daleks' Aubrey Woods in Willy Wonka and the Chocolate Factory 

Russell T Davies, Steven Moffat, Jenny Colgan and Anthony Dry book signing at Forbidden Planet