New caper movie Gambit's small budget left Colin Firth red-faced during filming, because he had to wander around half-dressed in front of real hotel guests.

The Brit stars as an art curator who is out to seek revenge on his boss by selling him a fake Monet in the new comedy, which co-stars Cameron Diaz and Alan Rickman.

In one scene, Firth's character is caught short without his trousers, and the actor had to walk around London's Savoy hotel improperly dressed in front of real guests because the film's budget did not stretch to paying to close down the venue for the shoot.

He tells Britain's Sunday Express, "Our budget meant we couldn't afford to ask the hotel to shut down for a few days, so we had to film while normal hotel life continued. The scenes requiring me to be incompletely dressed caused quite a few raised eyebrows from people who didn't realise what was going on.

"There was one rather inebriated lady whom I met, trouserless, in the revolving door of the lobby. I decided to just brazen it out, had a little chat with her and moved on."