The next series of Doctor Who could be David Tennant's last, according to Catherine Tate who appears as his assistant Donna in the sci-fi series.
Talking on a BBC radio show, Catherine said of the fourth series, which is due to hit our screens in spring 2008: "I think it's maybe David's last series."
The BBC has refused to comment on David Tennant's future in the show.
He'll be back for three Doctor Who specials in 2009, but after that no-one knows if he'll return to the tardis.
Catherine Tate also confirmed that the forthcoming series will be her last.
Kylie Minogue stars in this year's Doctor Who Christmas special
In September, it was announced that the fifth series wouldn't hit our screens until 2010.
It was thought that the delay was to allow David Tennant the chance to return to the stage with the Royal Shakespeare Company.
He'll be playing Hamlet from August 2008, which is normally when filming for the next series of Doctor Who starts.
In the meantime, fans can look forward to the Christmas special featuring Kylie Minogue which will be shown on Christmas Day.