By Tim Masters
Entertainment correspondent, BBC News
David Tennant is handing over the Tardis keys to Matt Smith
David Tennant said he had to keep a "stiff upper lip" while filming his final scenes for Doctor Who.
"It was very emotional saying cheerio," Tennant said after a screening of latest adventure The Waters of Mars, to be shown on BBC One on 15 November.
"There's lots of scenes in the final episode that are very sad, and were very sad to play."
He added: "On the actual final day I was a bit of a puddle, but kept a mildly stiff upper lip."
The Scottish actor, who took on the role of the Time Lord in 2005, admitted he had been "nervous" about seeing another actor on the role.
"I'm thrilled that it's carrying on," he said, "and know that everyone who's there is a great choice, but of course you feel a bit proprietorial."
Tennant is being replaced by actor Matt Smith, 27, who will appear as the 11th Doctor next year.
David Tennant and Russell T Davies on their final adventures with Doctor Who
The Waters of Mars will be followed by two episodes over the Christmas holiday that will see Tennant's Doctor once more pitted against The Master, played by John Simm.
The Waters of Mars is set on the Red Planet in the year 2059, and co-stars actress Lindsay Duncan as Adelaide - the commander of Earth's first off-world colony.
Tennant agreed that it was "probably" one of the scariest Doctor Who episodes.
"It tells a different sort of story. We expect the Doctor to take control earlier," he said.
The show's outgoing executive producer and lead writer Russell T Davies said: "It's not so scary as intense."
The episode is dedicated to Barry Letts, the producer of Doctor Who throughout the Jon Pertwee era of the early 1970s, who died earlier this month.