Screenwriters Steve Lewis and Tony Owen evidently disagree, contriving a comedy of errors about a beleaguered London Tube driver who can earn a sizeable compensation package if he can persuade someone to leap in front of his train. Even the most skilled scribes would struggle to navigate the thorny and sensitive moral dilemmas at heart of Three And Out and, regrettably, Lewis and Owen aren't up to thetask, clumsily melding a farcical opening 30 minutes with the heart-rending emotions of the downbeat finale. It's no wonder that rail union Aslef protested the premiere.

The sombre musings of the second hour proves strangely compelling, by virtue of a tour de force supporting performance from Imelda Staunton that is far better than the film deserves, but crass running gags continue to spoil the mood.

London underground driver Paul Callow (Mackenzie Crook, pictured) is shell-shocked when a passenger falls on the track in front of his train. A few days later, a heart attack victim suffers the same fate and Paul is surprised to learn from colleagues Vic (Mark Benton) and Ash (RhashanStone) about an unspoken rule: if a driver witnesses three accidental deaths within the space of one month, he is immediately compensated with ten years' salary.

The cogs of Paul's febrile imaginative whirr into action and he hatches a daring plan to find someone willing to throw themselves under his train for the money.

Deeply depressed Tommy Cassidy (Colm Meaney), who attempts to leap to his death off Holborn Viaduct, seems to fit the bill and the suicidal man agrees to Paul's plan on the proviso that they travel to the Liverpool so that Tommy can bid farewell to his loved ones. As friendship blossoms between the two men, Paul begins to question their macabre scheme but as Tommy reminds him, "a deal is a deal".

Three And Out is populated with crazed characters like a cannibalistic French chef (Antony Sher) and a foul-mouthed mistress (Kerry Katona), who distract from the film's half-hearted efforts to provoke debate.

Crook is a vapid leading man, unable to find any emotional depth to his loner, while Meaney's performance only gathers steam when the film reaches the Lake District and Staunton's embittered wife. Comedy and tragedy are unruly bedfellows and first-time director Jonathan Gershfield is poorly equipped to strike the right tone, lurching between extremes, often in the same scene.

Dialogue occasionally delivers some pithy home truths - "Isn't it a sin to commit suicide if you're Catholic?" wonders Paul; "Isn't it a sin to deliberately run someone down in your train if you're a human being?" counters Tommy - but piercing insights into the human condition are far beyond this film's grasp.