DAVID Tennant and Billie Piper are reunited on the set of Doctor Who after some time - and their rapport continuums.
They laughed and joked as they filmed the Christmas Special - after a year enjoying their own space.
Billie, 26, took a break from playing side-kick Rose to become a mum to Winston, now seven months old. And she filmed the third series of Secret Diary Of A Call Girl.
An onlooker at the south London set said: "Billie and David were joking about and seemed delighted to be working with one another again.
"They've got a natural chemistry. They get on so well."
The Christmas special, featuring The Doctor's old adversaries The Ood, will be 38-year-old David's last but one appearance as the 10th Time Lord.
He announced last year that he will leave the BBC show at the end of 2009 after completing three full series.
David took over from the previous Doctor Christopher Eccleston in 2005. David's final episode will be aired on New Year's Day, when he hands over to Matt Smith, 26.
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