Arnold was named best British director, with the best supporting actor award going to Michael Fassbender. Newcomer Katie Jarvis received the NSPCC Award for young British performer of the year.
Kathryn Bigelow took the director of the year award for her Iraq war drama The Hurt Locker; while Swedish horror Let the Right one In won foreign language film of the year.
The In The Loop team - Jesse Armstrong, Simon Blackwell, Armando Iannucci and Toni Roche – won the best screenplay award, while Duncan Jones won the breakthrough British film-maker award for science fiction Moon.
Quentin Tarantino, who attended the ceremony at the Landmark Hotel in London last night, won the Dilys Powell Award for excellence in cinema. The awards are held in aid of the National Society For The Protection
Jason Solomin, chairman of the London Film Critics Circle, said: “This was a brilliant night for both British and international cinema. It’s hugely significant that the London critics awarded film of the year to the French film A Prophet. This is a victory for world cinema and shows a refreshing open-mindedness to judge all film on equal footing, from giant Hollywood blockbusters to classy European prison movies.”