Over the years, there have been ten Doctors, starting with William Hartnell in 1963, up to David Tennant, who will play the Doctor until 2010, when Matt Smith will take over.
Inside sources at the BBC production team responsible for bringing back have revealed a long term trend that they are attempting to continue, which gives some indication of where the series will be going.
"Hartnell was nearly a hundred when he played the Doctor," said a prominent member of the production team who wishes to be called David Trussel, to maintain anonymity. "Whilst Tennant was a mere whipper snapper at thirty-four. There has been a downward trend of ages, and Matt Smith is only twenty-seven. I have a Now! album older than that."
Hartnell was actually fifty-five when he first appeared as Doctor Who in black and white back in the early sixties. Not many people realise that to save money, the original Tardis was actually unpainted cardboard, they just told everybody it was blue. Apart from Peter Davison (not Davidson, as many people call him), there has been a definite downward trend. Davison bucked the trend being just thirty when he donned the celery and hat that would be his trademark for three years.
"I've still got that celery," said Davison. "They actually wanted Robert Hardy to play the Doctor, but a mix up at the All Creatures Great and Small production company meant I got sent along instead. I'm glad it did, it got me a part in Magnum PI!"
With the trend now identified, where will it end?
"We've got a contract until 2050 with the BBC," said Trussel. "Assuming we continue going through actors at the current rate, the person who will play the twentieth doctor will be fourteen. He hasn't even been born yet!"