To be fair, if it were secret, you wouldn’t know it. The rumour is saying that it’s been dressed up as filming for Horrible Histories.No real effort was made to keep anything from the production shoot of the Centenary Special secret, so there's no way that the Bakers, Davison, and McCoy being on set would've gone unnoticed.
indeed. It doesn't make a lot of sense, surely they'd be better placed for the 60th, and assuming it isn't just complete BS which is highly likely, maybe someone is getting their specials mixed up? Irrespective of the plausibility of their appearing, the logistics are eminently possible, hell anyone could cameo for all we know, William Russell, Janet Fielding, Sophie....anyone (who's still with us obviously)