As many of you will know, UNIT is an international taskforce, first introduced into Doctor Who back in 1969, when Patrick Troughton was playing the Doctor. Then, when Jon Pertwee took on the role, the Doctor became UNIT's scientific advisor. Since then, UNIT has appeared off and on in the TV series, right up until last weekend in the TV episode The Power of Three (starring Matt Smith).

A few years back, Big Finish released a UNIT series, and due to popular demand, here's the follow-up. But this time round, it's a very different kind of story. The Seventh Doctor (Sylvester McCoy) features with companion Raine Creevy (Beth Chalmers - introduced in Doctor Who: The Lost Stories) along with several brand new UNIT characters, including Colonel Lafayette (pictured, played by Julian Dutton) and Major Wyland-Jones (Samuel Clemens).

Also featuring are Dr Elizabeth Klein (who originally featured in Doctor Who: Colditz, then returned in a trilogy of adventures beginning with Doctor Who: A Thousand Tiny Wings) and a brand new incarnation of the Doctor (played by Alex Macqueen).

'It's quite a dizzying line-up of main characters,' says director and co-writer Nicholas Briggs. 'Klein was first introduced as a Nazi from an alternative future in Colditz, but now she has a new role as UNIT's scientific advisor... and she has real issues with the Doctor - both of him!'

And as for this new Doctor himself... 'Well, he's an interesting character, played to perfection by Alex Macqueen,' says Briggs. 'I won't give too much away, but this new trailer will give you a flavour of what to expect.'

Doctor Who: UNIT - Dominion is available to order now at a special bargain rate - but hurry, as it reverts to full price when it's released in October. It's also available as part of a Special Releases bundle for a further discount, if you purchase it alongside Doctor Who: Love and War (the Seventh Doctor, Ace and Bernice Summerfield), Doctor Who: Dark Eyes (the Eighth Doctor and the Daleks), Doctor Who: Voyage to Venus and Doctor Who: Voyage to the New World (both featuring the Sixth Doctor and Jago and Litefoot).