Spoilers! The Next Doctor

The plot has been kept under wraps until now, but Tennant told BBC Radio 5 Live: "The Doctor's on his own now and he lands in Victorian London and meets a future version of himself played by David Morrissey - who else would you want to cast as the Doctor, really? It's sort of perfect casting - but this Doctor, this future version of the Doctor doesn't seem to know who the current Doctor is, so clearly something has gone a bit wrong. He's had a memory lapse and is in a bit of a difficult state, that's got something to do with the fact that he's fighting the Cybermen at the time."

Read more at: telegraph.co.uk