Tommy, innocent and fearful, meets a French soldier, and they desperately carry an injured man on a stretcher toward the shore. Theirs is not a noble act. They are pretending to be medics in the hope of getting on a ship and saving themselves, which instantly sets Dunkirk apart from simpler, hero-driven war movies.

Rylance’s character, Mr Dawson, is part of the day-long sea action, in which hundreds of small boats are called on to help. Dawson’s young adult son and a teenaged friend are also on board. Cillian Murphy later joins them as a traumatised soldier rescued from the sea. But it is Rylance who carries the emotional weight of the movie on his wrinkled, weary face, full of determination and simple decency. He brings a depth beyond the lines written into the script.

War laid bare

Nolan has said that the inspiring story of the little ships was something he, like many in Britain, grew up with in its ‘almost fairy-tale form’. The ‘Dunkirk spirit’ may be more familiar in the UK than elsewhere, but that is no obstacle. The film resonates in purely human terms, as Nolan strips away the myth to reveal a complex reality, and many different forms of heroism and of fear.

The air battle, which covers only an hour, has Tom Hardy and Jack Lowden as RAF fighter pilots. When his fuel gauge fails, Hardy’s character must rely on radio contact with Lowden’s, guessing whether he’ll have enough fuel to get his Spitfire home.

It is Mr Dawson who uses the apt phrase “sitting ducks.” All these characters are under fire from the air, as Nolan conveys a sense of extreme vulnerability. To shelter themselves from gunfire overhead, soldiers on the beach can do little more than fall flat on their faces. Boats, big and small, are sunk. The hull of a ship begins to fill with water and people who have supposedly been rescued have to fight their way out. One of them is played by pop star Harry Styles, as a quick-tempered soldier. Styles has a vibrant presence on screen, but his fans should know this is a small part.