Here is what I know so far...you bad, bad Whovians;-)
One photograph shows the tenth and eleventh Doctors being interviewed outside the Tardis, while in the background a Zygon!!!
The classic Doctor Who monsters, last seen in an onscreen adventure in 1975, were revealed to be part of the celebration episode earlier this month.
The scenes being filmed at Chepstow Castle in Wales this week look as if they are set during the British Civil War, with guests stars including Gavin & Stacey's Joanna Page, and various extras, photographed wearing medieval costumes.
Between takes, Smith and Tennant were seen chatting together and signing autographs for fans.
The Doctor Who 50th anniversary special also stars Jenna-Lousie Coleman (spotted on set below), who plays current companion Clara, and the tenth Doctor's partner in time, Rose Tyler, played by Billie Piper.
An air date for the episode has not yet been revealed but the first ever Doctor Who adventure was broadcast 50 years ago this November.