The Intergalatic Alliance has changed considerably since Mission to the Unknown. All the actors who played the aliens have been replaced and many of the costumes have been modified or completely reworked.
With the return of this episode to the BBC in January 2004, it brought the total number of missing episodes down to 108.
Was made available with the DVD release of the William Hartnell Lost In Time collection, as well as the boxed set. This would be the first time the mass market had the chance to see this episode since it aired in 1965.
Before the discovery and return of Day Of Armageddon, very little visual reference material existed for several characters in the episode and serial as a whole. Only one low quality photo, in a private collection, of the alien Celation was known to have existed prior to this.
Was returned to the BBC vaults in January 2004. Survived because of one Francis Watson, the Head of Engineering at Yorkshire Television in Leeds. Working for the BBC in the early 1970s, he was supposed to clean out a room full of junk at the BBC's Television Film Studios in Ealing. Watson saved two 16mm film cans marked Doctor Who, so that he could watch them on the projector at his local film club. Watson's little act of pilfering saved this episode from being lost forever, so he is easily forgiven. Interestingly enough, Parts 5 and 10 of this serial were also discovered in junk piles intended for trashing in the mid-1980s.