Jonny Lee steps up to the mike

It's a gangster movie, but as opposed to face-offs with broken bottles, it's about seeing who's best on the old microphone at the karaoke.

And the gunfight scene, with me gunning for Rhys Ifans and Sean Pertwee, is particularly hysterical because nobody gets hurt. Basically they're like most criminals - ordinary people doing, er, illegal stuff.

Ray Winstone is head honcho of the North London mob I worm my way into through his nephew, my best friend since primary school, played by Jude Law. I see him as the way out of my dead-end courier job. Part of the appeal to play him, apart from the karaoke of course, is because he is extremely unlikeable. He has some underlying psychotic tendencies and I based him on a real postman who re-invented himself as a gangland killer.

The singing was such a laugh. I do the old Tony Christie number, "Avenues And Alleyways". Dominic Anciano, who wrote, directed and produced the film with Ray Burdis, thought it was a brilliant tune and originally the whole film was going to be written around it. I knew the song inside out because we played it 24 hours a day at Dom's house and I pleaded to be allowed to do it. Kathy Burke plays Ray's wife and Denise Van Outen is Dom's girlfriend.

The film is entirely improvisational - very scary but something you never get to do in our job so a chance you just couldn't throw away.