DOCTOR Who David Tennant is dating his co-star Georgia Moffett - who played his on-screen daughter.
The Scot and Georgia, 23, were spotted leaving his house in London together at the weekend after spending the night there.
David travelled to Georgia's Twickenham home on Saturday night and didn't leave until Sunday morning.
The relationship will shock fans who saw Georgia play the Timelord's daughter in an episode of the current series just last month.
More incredibly, the single mum is the real-life daughter of 1980s Doctor Who, Peter Davison.
David, 37, has even made friends with his new girlfriend's six-year-old son Ty.
A pal of Georgia's said: "They have been going out together for a while now but meet up at each other's house so as to avoid being spotted by Who fans.
"David can't go anywhere without attracting attention and it's early days so they don't want any distractions or fuss made about what's going on.
"It started with some friendly dinner dates but has progressed quickly and they are now in a serious physical relationship.
"They look really cute together and Georgia is very happy at the moment.
"Even with his busy schedule, David is making a lot of time to spend with her, so he must really like her."
The couple met while filming scenes together in Wales last year and there was instant chemistry.
In the script, Georgia's character Jenny is shot in the chest and the Doctor cradles her and kisses her head.
She later blasts off into space alone, making it possible to return in future episodes.
In the run-up to the episode's screening, Georgia told how Tennant was the perfect gentleman on set, saying: "It was winter in Cardiff when we filmed and I was wearing very little so you can imagine how cold that was.
"David kindly lent me his jacket between takes. I put it on, bent over and ripped the back of it."
Georgia has recently been filming Spooks: Code 9, a spin-off of BBC series Spooks.
And Tennant began rehearsals yesterday on his version of Hamlet for the Royal Shakespeare Company.
He is unlikely to be phased by the 14-year age gap in his current relationship.
He recently said: "I still think of myself as 18."