Trafalgar Tardis

They seem to be filming Doctor Who in Trafalgar Square today, from what I could find out it's part of the filming for the 50th anniversary episode due soon.

Also, the stunt double under the Tardis is dressed in an older Doctors outfit by the look of it so this is part of the look back story line, I guess.
This is Matt Smith's (who currently plays the Timelord ) stuntman and was later spotted dangling from the Tardis attached to the crane you can just see.

And the Doctor's companion Clara (Coleman), was also seen poking her head out of the Tardis's door.