Jenna-Louise Coleman (Clara) and Jemma Redgrave (Kate Stewart) feature in the location report from the Tower of London.
The new clip also confirms the addition of actress and comedian Ingrid Oliver to the cast of the 50th special.
Oliver - seen sporting a scarf reminiscent of that worn by Tom Baker's Fourth Doctor - is perhaps best known as one half of the comedic double act Watson & Oliver.
A second video - featuring Who lead Matt Smith and the filming of a stunt sequence - has also been released.
Filming on the Doctor Who anniversary episode is currently 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.
> Doctor Who 50th: BBC denies Christopher Eccleston 'quitting' rumours
> Sylvester McCoy on Who 50th: 'Past Doctors haven't heard anything'
Gallery - Doctor Who's next episode 'Cold War' in pictures: