Fans of Doctor Who are speculating whether it is time for a woman to step into the role.
Actor Matt Smith is to leave the BBC TV series after a 50th anniversary show in November.
Bookmaker William Hill was offering odds of 8-1 on the next Dr. being a woman. Suggested actresses include Billie Piper, who played Rose Tyler a few years ago, Tilda Swinton and Olivia Colman.
Ladbrokes was offering odds of 20-1 on Helen Mirren.
But the chance of a female Dr. Who remains a long shot.
William Hill had its joint favourite replacements at 10-1 as Rupert Grint of Harry Potter fame and Russell Tovey who appeared in a couple of Dr. Who episodes.
Ladbrokes' favourite at 3-1 was Rory Kinnear, son of Roy Kinnear.
The series began in 1963 and is now broadcast in 48 countries with 77 million viewers in Britain, the United States and Australia alone.
The role was previously played by William Hartnell, Patrick Troughton, Jon Pertwee, Tom Baker, Peter Davison, Colin Baker, Sylvester McCoy, Paul McGann, Christopher Eccleston and David Tennant.