Wondering what else he might get out of life as retirement approached, a crane operator in the English port city of Barrow-in-Furness took up the game of golf. As you do. Then when a champion golfer demonstrated his moves one day on his new colour telly, Maurice Flitcroft thought, I can do that too. As you do.

A man with big dreams but modest means, he couldn't afford the fees at the local golf club so he borrowed books for golfing beginners from the local library and took to the beach to practise. There wasn't much of that and not even a handicap, but in 1976 Flitcroft entered himself in the British Open, where he earned a reputation as the worst golfer of all time.

The real, undaunted Flitcroft, played here by Mark Rylance, was a man of unsinkable brio. He entered the Open again and again in disguise and under jaunty pseudonyms like Gene Pacecki. He has gone down in sporting history as an audacious hoaxer. It could never happen now, or could it?

Like the film's titular reference to the longest-running Broadway show ever, The Phantom of the Open tells the story of a real-life show that just kept going and going - Flitcroft the golf fanatic who couldn't hold himself back from the big stage.

What a gift of a role for Rylance, so memorable and variable on screen in Wolf Hall, as a Soviet spy in Bridge of Spies and as a big friendly giant (The BFG). The actor's mastery of this comedic role as a dimwit and a dreamer with plenty of chutzpah is something new again. As one of life's true eccentrics, Rylance made me laugh, again and again, till I cried.

We can't assume that behind every unassuming, chain-smoking crane driver there's an irrepressible extrovert struggling to get out, but as shipyard fodder what kind of life was it? In on your feet and out in a box? As one of life's dreamers, Maurice didn't need much encouragement to give competitive golf a go from his drinking partners at the pub, or his loving, indulgent wife, Jean (Sally Hawkins).

Sally and Maurice's sons, Gene and James, were also onboard and even caddied him. Identical twins Christian and Jonah Lees are funny and engaging as the disco dancers who became minor celebs in their own right in real life, inside the brief window the disco craze offered them.

Despite catchy Bee Gees hits playing in the background of family scenes of happy, domestic chaos, their elder brother, Michael (Jake Davies), is the odd man out. Sally's son by an earlier relationship is very put out about the golfing adventure. It gives him all sorts of grief at work in his job as an aspiring management material. There he was, studying for an engineering degree and doing the proper thing by getting a real job, while his kid brothers, the dancing duo, were cavorting and carrying on, aided and abetted by their father.

The Phantom of the Open, directed by Craig Roberts, is based on a screenplay by comedian Simon Farnaby adapted from his biography of Flitcroft and co-written with Scott Murray. They are all entirely on-side with their subject, even devoting some childlike animations as we travel inside Maurice's head and share his day dreams. Much of the aesthetic of The Phantom resembles the colourful, brash aesthetic of 1970s television. A very good fit, after all.

It wasn't the quixotic forays into professional golf that were weird, it was the rest of the world, in particular the golfing establishment, represented by Rhys Ifans' Keith Mackenzie, the villain of the piece. Eventually, Flitcroft was banned for life, but in this take on the man, the golfing public, if not the other players, warmed to their relatable folk hero.

As the film has it, Flitcroft met Severiano Ballesteros, an upcoming 19-year-old, at the British Open. Flitcroft leans over to shake hands with the young Spanish player who introduces himself as Seve, though Maurice remains none the wiser in this jaunty takedown of the sporting establishment.

There are many playful ideas at work here in this lively comedy in the British tradition that celebrates life's eccentrics, from the film The Duke to The Lavender Hill Mob. All in very good fun.