The City of the Daleks has been revealed as the first of four 'interactive episodes' of Doctor Who, which the BBC is offering to web users. 

Doctor Who: The Adventure Games, which were announced earlier this month, have been developed by Sumo Digital and are free to download.

Compatible with both PCs and Mac, the games feature voiceovers by the cast, along with music created by the show's composer Murray Gold.

The City of the Daleks takes place in London in 1963. However, the UK's captal is in ruins after being taken over by a new breed of Daleks, which were seen for the first time in the TV show the previous weekend.

PC users must guide the Doctor on a quest to the Dalek's home plant Skaro in a bid to save Earth.

"City of the Daleks is as big-budget as you can imagine: from London we head to Kaalann, the capital city of the Daleks, one constructed from pure anger and hate," says Doctor Who writer Phil Ford.

"These new Daleks don't like to be messed with, so players are about to enjoy a new interactive episode which is as heart-pulsing as anything you've seen before."

Doctor Who: The Adventure Games 'City of the Daleks' will be available to download for free from the Doctor Who website from June 5.

See also: BBC iPhone apps put on hold