'He told people what they needed to hear': The weatherman crucial to D-Day victory

It was the boldest military operation in history – and its success hinged on weather forecaster James Stagg. A new film with Andrew Scott and Brendan Fraser explores his role in the end of World War Two.

On his inauguration day, in 1961, John F Kennedy asked the outgoing president, Dwight D Eisenhower, what had given him the advantage over the Nazis on D-Day, when Eisenhower was Supreme Commander of the Allied Forces. "We had better meteorologists than the Germans," Eisenhower said. That anecdote is cited at the end of the new film Pressure, which suggests that Eisenhower's reply was not much of an exaggeration. The film tells the true story of the life-or-death decisions the Allies' chief meteorologist, Scottish Royal Air Force Captain James Stagg (Andrew Scott), and Eisenhower (Brendan Fraser) had to make in the three days leading up to the Allied invasion of Normandy, which historian Antony Beevor, in his authoritative D-Day: The Battle for Normandy, calls "almost certainly the most ambitious operation in the history of warfare".  

As events unfolded, on 6 June 1944, nearly 160,000 Allied troops arrived in Normandy by air and sea, which proved to be a turning point in the war. But days before the landing, which was initially planned for 5 June, Stagg could see that a dangerous storm was coming, even though the team of meteorologists he led disagreed with him fiercely. His job was to distil the forecasts into a simple Go or Don't Go recommendation for Eisenhower. But it was fraught with pitfalls: going into a storm could have cost thousands of lives, but a delay could have meant waiting weeks for the right conditions and risked word of the operation leaking to the Nazis.

Based on David Haig's acclaimed 2014 play, the film turns those events into a tense drama full of clashing opinions and egos. And as its creators tell the BBC, it is also a story about relying on the hard evidence of science, and the heroism of telling uncomfortable truths.

"How do you make a slow-moving weather system feel thrilling? It's not just the weather," the film's director, Anthony Maras (Hotel Mumbai), who wrote the screenplay with Haig, says. "How do we look at the characters, put them under immense pressure, and see how they morph and change?" From that perspective, he says, "You can make a film about a slow-moving weather system feel like the biggest thing on Earth because it is to these characters."

Scott portrays Stagg as historical accounts do: a taciturn, buttoned-down personality. He had, Haig says, "a quiet, steely integrity", and Scott allows us to see the depth of feeling beneath the brusque exterior. Much of the film takes place in offices and rooms full of weather maps in Southwick House, the 19th-Century estate near Portsmouth used as Allied headquarters,........

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