★★★★

British director Ken Loach has been standing up for the underdog since Cathy Come Home, his screen debut 50 years ago. And it could get boring.

It doesn't – because of his passion for the particular. Every film he makes is enlivened by his fascination with the mechanics of the injustices which fire him up.

Bureaucracy has always been a cherished irritant and he's learnt a lot during his decades of doing battle with it. Among the many attractions of the beguiling I, Daniel Blake - winner of the Palme d'Or at this year's Cannes Festival – is his gift for gallows humour.

It's a film full of wit and common sense, along with a stroke of genius in the casting department. For the role of Daniel, a 59-year-old Newcastle carpenter unfortunate enough to suffer a heart attack at work, Loach has chosen Dave Johns, a stand-up comic and occasional actor who faces the labyrinthine British welfare system with a despair mixed with wonder and amusement. Dan certainly doesn't welcome the bureaucratic education he has been forced to undergo but he does treat it as a learning curve. He is determined to unravel the mysteries of a system that has disregarded the opinion of his medical team and deemed him fit for work and so, ineligible for sickness benefits.

Loach and screenwriter Paul Laverty – his long-time collaborator and an even more diligent researcher than Loach – have interwoven the complications of this predicament with the story of Dan's friendship with Katie Morgan (Hayley Squires), a young single mother with two children, whose struggles with the system mirror his own. They meet at the Jobcentre, where she's being penalised for arriving late for her interview because she is new to Newcastle and got lost on the way.

It's not all gloom and frustration. There's a genuine camaraderie, with no trace of the romantic, in the scenes between these two. It's touching to watch them bolster their self-esteem by finding ways to help one another. And Dan has another supporter in his irrepressible young neighbour China (Kema Sikazwe), who has earned his nickname because he's exercising his entrepreneurial talents by selling black-market sneakers from China. He's the one who helps Dan over a seemingly insuperable obstacle – the completion of a Jobcentre form which can be done only online.

It's the absurdities which bring out the best in Dan. His every Jobcentre interview becomes a duel in which he can't resist pointing out the inconsistencies of a system which seems designed to make ciphers out of those who depend on it and those who administer it. After his last film, Jimmy's Hall, Loach was heard murmuring about giving up feature filmmaking. I'm very glad he changed his mind.