Guy Ritchie is a ''grumpy old bastard'' when he's drunk.

The 46-year-old director has confessed he isn't much fun on set when he's tired or hungover but insists it has never caused him to get angry at anyone who he works with because he doesn't think it's conducive to a good working relationship.

He explained: ''I can be a grumpy old bastard if I've drunk too much and stayed up too long. But I don't think I've ever lost my temper on set - my suspicion is, if you do it once, you'd do it again.

''I'm very selfish, in the sense that I'm out to tick certain boxes. The first being that I want to enjoy myself - I'm only interested in having a good time. I'm not interested in arguing, so I never understand why people get their knickers in a twist on a film set. It's a fantasy job, but you'd be surprised how many people forget that.''

However, the star - who recently tied the knot with Jacqui Ainsley - admitted he regularly got inebriated while making his most recent movie 'The Man From U.N.C.L.E.' in Italy and he was still able to make a good film.

He told Shortlist magazine: ''Well, we were filming in Rome, which was five weeks of absolutely full-on boozing and eating. In terms of indulgence, it was like Ancient Rome. Somehow, we all came back slightly thinner than we were, and we can't work that out. Everything they say you shouldn't do, we did, but everyone came back lighter. And you'd be surprised how you can go to work on a few bottles of chianti [wine] but still manage to make something that makes sense.''