The visual effects company were rewarded for their work on The Pandorica Opens.
The the RTS explained:
"The judges were impressed by some beautifully integrated effects and by green screen. 'This is about as good as it gets on TV' they said."
Steven Moffat and Mark Gatiss's Sherlock won three awards; best picture enhancement, best tape and film editing in a drama, and best original title music.
The Mill have also produced visual effects for Torchwood and The Sarah Jane Adventures.