Is David's future as The Doctor in doubt?

David Tennant's appearance in a fifth series of Doctor Who looks uncertain after it was announced that the next run of the sci-fi show will be postponed until 2010.

With the fourth series due to hit TV screens next year, viewers would expect to see a fifth series in 2009 - but the BBC have announced that the show will not return until a year later.

In the meantime, 36-year-old David will star in three Doctor Who BBC1 specials, written by Russell T Davies, in 2009.

The fifth series has been postponed so that the Casanova star can take to the stage to play Hamlet with the Royal Shakespeare Company from July to November next year.

A Doctor Who spokeswoman said of whether Tennant would be returning to the Tardis for a fifth series: "It's too early to comment."

The Scottish actor took over from Christopher Eccleston after he quit the revival of the show after just one series in 2005 despite its enormous success.

The fourth series, which is in the process of being filmed, will see David with new assistant Catherine Tate, who follows on from Freema Agyeman - also set to return - and Billie Piper.