Between filming the twin swords and sandals epics Troy and Kingdom of Heaven in Malta and Morocco in 2004, much-in-demand Dublin-born actor Brendan Gleeson nipped home to Ireland to make a short film called Six Shooter. A comparatively modest project in every sense – no other well-known actors, first-time director, no budget – the 27-minute long film went on to win the 2006 Oscar for Best Live Action Short. Two years and two appearances in Harry Potter films later Gleeson has reunited with Six Shooter’s writer-director, the Anglo-Irish playwright Martin McDonagh, to make the man’s feature film debut, In Bruges. It’s a black comedy about a pair of professional hitmen (one played by Gleeson, the other by Colin Farrell) who are sent to lie low in the medieval Belgian city after a job in London goes wrong. The film plays like Waiting for Godot meets Reservoir Dogs.

‘I went there and was struck by how beautiful the city was,’ says 38-year-old McDonagh. ‘But I was surprised it had never been used in a film before, because it was very iconic. I was walking round and these two characters just popped up in my head: one guy who hates the place and one who loves it. When I got back to London I had the idea these guys should be hitmen, and everything else came from that.’

‘Martin’s work is robust yet delicate,’ Gleeson says. ‘You have this combination of the worst of humanity and yet a feeling of connection to these people. They’re all too human. And that’s a challenge for an audience and an actor.’

McDonagh’s also well-known in theatre circles. He’s twice won the Olivier Award and been nominated four times for a Tony. His six stage plays and two radio dramas combine dark tragedy and black humour (The Lieutenant of Inishmore, for example, concerns the leader of an IRA splinter faction who goes insane when his cat is killed) and have earned McDonagh a reputation as one of the progenitors of ‘in your face’ theatre. That tough but comic tone has been carried over into In Bruges, which hinges upon generating sympathy for and laughs from the foulmouthed murderers.

‘That’s where Brendan is key to this film,’ McDonagh says. ‘He conveys great strength and compassion, and shows you that a warm-hearted hitman does not have to be a contradiction in terms. This is a film about violence, loyalty and honour, but it also catches the innocence in and great affection between the two men, and finally it deals with an opportunity for redemption.’

The film’s themes may overlap with McDonagh’s theatre work, but In Bruges is very cinematic in terms of the use of its Flemish locations, the atmospheric photography, low-key performances and the rapid-fire editing. But, as Gleeson notes, McDonagh has always professed to be primarily influenced by Scorsese, Lynch and Tarantino. ‘He’s been a keen student of film all of his life,’ says the 53-year-old, who gave up teaching for screen acting 20 years ago. ‘And I think his plays are very cinematic. So, when we were making Six Shooter I could tell Martin knew what he was doing. On In Bruges he was even more confident. So there were no nerves on my part in working with a first, now second time director.’

In Bruges is on general release from Fri 18 Apr.