Smith was seen performing a dangerous stunt for the anniversary episode, dangling from the bottom of a TARDIS prop.
Two short videos were released earlier today by the BBC - in the first, Coleman, Redgrave and comic Ingrid Oliver are seen on-location at the Tower of London, while in the second, Smith prepares to shoot his airborne stunt.
Filming on Doctor Who's 3D anniversary episode is ongoing under director Nick Hurran.
Returning stars David Tennant and Billie Piper will appear opposite Smith, while confirmed guest stars include John Hurt (Alien) and Joanna Page (Gavin & Stacey).
Doctor Who continues this Saturday (April 13) at 6pm on BBC One.
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Watch the stars of Doctor Who talk the 50th special with Digital Spy below: