DAVID Lowery’s comedy drama starts in a style to which you will soon become delightfully accustomed. “This story, also, is mostly true,” is the wry pledge on screen. In gently mocking the endless trail of stories drawn from reality, The Old Man & The Gun is confidently setting up its stall. We know you’ve heard some yarns, says the film with a twinkle in its eye, but this is a doozie. It certainly is.

Indeed, perhaps the only thing wrong with the picture is that it arrives tinged with melancholy. The film’s leading man, Robert Redford, has said this will be his last outing as an actor. The Sundance Kid is now, brace yourselves, 82-years-old, and feels it is time to go behind the camera and stay there. Having never won a best actor Oscar, he has one for directing Ordinary People and an honorary award, this could be his last chance. So no pressure, Academy.

It is Texas, 1981, and a smartly dressed gent of a certain age is leaving a bank, having just made a satisfactory transaction. He has asked the teller to hand over the money in the till, they have done so, and not a shot has been fired. As he drives along, all the while listening to the police radio, he sees a woman with car trouble and stops to help. Is he being genuinely kind, or does he simply want to hide his head in a car bonnet while police cars fly past? It is the first of many times we will wonder about “Bob’s” motives.

His chivalry merits a coffee with Jewel (Sissy Spacek), and conversation turns to what he does for a living. I’m a bank robber he teases, and to prove it talks her through how he would rob the diner they are in, winding up the story by saying he is just pulling her leg. With the light on his face, Redford looks every minute of his age, but what a charmer.

Across town, detective John Hunt (Casey Affleck) is being forced to celebrate his 40th birthday. Married with two children, Hunt is worried his career is going nowhere. It hasn’t helped that he was in a bank that was being robbed by Bob and did not notice a thing. His pride hurt, Hunt resolves to catch the thieves.

As he follows up past cases a pattern emerges of three old guys, one a real gent, pulling off slick heists. “It’s a funny story,” begins one officer. “Nothing funnier than armed robbery,” deadpans Hunt, thereby drawing attention to the moral tightrope the film must walk. Bob and his equally vintage accomplices (Danny Glover, Tom Waits) might be nice guys after a fashion, but they still terrorise staff into handing over other people’s hard earned money.

Lowery (Pete’s Dragon, Ain’t Them Bodies Saints), working from a story broken by David Grann in the New Yorker, gets away with it through a clever telling of the tale which keeps just enough back while sowing the right amount of doubt. His ultimate, not so secret weapon in getting the audience on side is Redford. Like the old man in Hemingway's tale, Bob is wrestling so hard with his nature that we want him to succeed.

There are surprises still to come as Hunt goes after the trio he dubs “The Over the Hill Gang”. In one glorious scene the cop and the villain meet, Affleck going head to head with Redford as if in some light comedy version of De Niro and Pacino in Heat.

Affleck is pitch perfect as the cop who talks a cynical game but holds tight to traditional views of right and wrong. Waits and Glover shine brightly around the tale’s edges, while Spacek is plain wonderful as a woman who knows the importance of doing what you love in life, and loving what you do.

For those who have lived through the many ages of Redford, which span all the way from the 1960s (Barefoot in the Park, Butch Cassidy and the Sundance Kid) to the 1970s (The Candidate, The Way We Were, The Sting, The Great Gatsby, All the President’s Men) and beyond (All is Lost), it is hard to think this will be his last acting hurrah. Great to see him going out, once more, with all guns blazing.