[ZeoRangerV]

Oh yeah, the official synopsis for the episode is out now too:

The Doctors embark on their greatest adventure in this 50th anniversary special. In 2013, something terrible is awakening in London’s National Gallery; in 1562, a murderous plot is afoot in Elizabethan England; and somewhere in space an ancient battle reaches its devastating conclusion. All of reality is at stake as the Doctor’s own dangerous past comes back to haunt him.

It's not really spoilery (its basically a TV Guide synopsis) but I thought I'd be courteous.