The final viewing figures for The Waters of Mars have recently been revealed by the Broadcasters Audience Research Board (BARB). The hour long special was written by Russell T Davies and Phil Ford and starred David Tennant as The Doctor alongside Lindsay Duncan as Adelaide Brook. The synopsis for the episode read: 'Mars, 2059. Bowie Base One. Last recorded message: "Don't drink the water. Don't even touch it. Not one drop." Starring David Tennant as the Doctor and guest starring acclaimed British stage and screen actress Lindsay Duncan, The Waters Of Mars is the second Doctor Who special to be screened this year. Lindsay plays Adelaide – the Doctor's cleverest and most strong-minded companion. She and the Doctor face terror on the Red Planet in one of the scariest adventures yet. Neighbours, Flying Doctors and Casualty star Peter O'Brien also guest stars as Ed, Adelaide's second-in-command at the base.' The special was watched by 9.94 million people across Britain, with additional ratings on BBC HD. The episode also achieved an official Appreciation Index of 88. Doctor Who will return this Christmas on BBC One, with The End of Time Part One, which is expected to get an even higher rating.