Steven Moffat spoke to BBC America on the red carpet of Sunday's BAFTA Awards and has talked of the great chemistry between David Tennant and Matt Smith whilst filming the 50th Anniversary Special.
"Matt and David together was quite special. They really, really, really got on well with each other and adored working with each other. It was just properly funny. The two of them together in particular are really, really funny"
When asked if it was the real Tenth Doctor or the alternative version that David would be playing Moffat simply says "I'm not telling you!"
Watch the full interview below: