Doctor Who returns for the second series since its 21st Century revival on BBC One on Saturday, 15 April.

As part of the BBC's drive to broaden the appeal of its top programmes, the Tardisodes will include footage that will not be seen on TV.

This will include meeting cat women in episode one who can cure all illnesses, and joining Rose's boyfriend Mickey as he discovers alien activity in a school.

Another gives viewers access to the Cybermen upgrade process.

The downloads, made in Cardiff by BBC Wales and BBC New Media, will be available a week before each TV episode.

The Tardisodes are part of a wider project, the BBC's TV Plus trials, which includes preview clips on mobile phones, programme premieres on broadband and other on-demand services through broadband and digital TV.

'Explore new worlds'

Each is created by the team behind Attack of the Graske, the 15-minute interactive story on digital TV which accompanied the Doctor Who Christmas special, which saw Tennant's first outing as the tenth Time Lord.

BBC director of television Jana Bennett said: "What better way of travelling with the Time Lord than to have a Tardisode come to you on your phone or PC?

"The Tardisodes are an exciting development, delivering mini-episodes which will let viewers access the vortex and explore new worlds before the Doctor arrives himself.

"We know that there is a huge appetite for Doctor Who and we want to make the whole experience bigger and better for viewers.

"These TV Plus trials will continue to help us understand more about the different ways in which viewers want to enjoy Doctor Who."

Although the downloads are free - the BBC does not charge for its mobile content - people will have to text the word TARDIS to 81010 to subscribe to the service.

A reply text will cost 12-15p and mobile phone users can expect to be charged for using the internet on their mobile phone.

Attack of the Graske attracted 496,000 viewers, with an average of 41,000 requests per week via the Doctor Who website.