The story is written and directed by Nicholas Briggs, who said:
We wanted to do a proper, fully-fledged multi-Doctor story for this very special occasion, and it's wonderful that all the surviving Doctors threw themselves behind the project so enthusiastically. That's not to say the first three Doctors don't appear – we wanted to pay homage to the whole history of the classic series.As well as the Doctors, popular companions will also be involved from each era: for Tom Baker's Fourth Doctor it's Leela as played by Louise Jameson; then for Peter Davison there's Nyssa (Sarah Sutton); for Colin Baker's era there's Peri (Nicola Bryant); Sylvester McCoy's sees Ace (Sophie Aldred); and from the Paul McGann Big Finish adventures there's Charley, as played by India Fisher.
And if that wasn't enough, producer David Richardson added:
Geoffrey Beevers is back to create mayhem as the Master, and there will be a number of appearances from some much-cherished old friends from the TV series . . .Released in November 2013, two versions of the story will be available: a standard two-disc release comprising just the episodes, and a limited edition five-disc release that will have two additional documentaries, plus Companion Chronicles tale The Revenants (performed by William Russell, previously available as a Doctor Who Magazine download).