Benedict Cumberbatch is set to appear in Peter Jackson's The Hobbit alongside Sherlock co-star Martin Freeman.
The pair were at the TV Baftas last night to recieve the gong for Best Drama series for Sherlock.
Backstage aftwards, Freeman was asked about his role in The Hobbit , and accidentally let slip that Cumberbatch had signed on to the film also.
When asked about his role, Cumberbatch remained mum; "I can't say at the moment, thank you very much."
An embarassed Freeman added; "I knew I was a sort of a big mouth but I didn't realise to what extent I was a big mouth, and I've just ruined everything.
"I might not actually go back to a job - they might have just sacked me."
Filming is currently underway for The Hobbit in New Zealand. Casting announcements are still appearing regularly throughout production, with Stephen Fry and Hugo Weaving confirmed in recent weeks.
Freeman, who plays titular Hobbit Bilbo Baggins in the two-part fantasy epic, is back in the UK briefly to film a second series of Sherlock, which will air later this year.
The Hobbit: Part 1 will be released December 2012.