WE Brits talk about the weather all the time. Will it be sunny for the weekend, the wedding, the village fete, the cricket …? Will there be enough rain for the crops? You name it, whatever we are planning to do, we want to know what the weather will be.

The Met Office is pretty good and the increased sophistication of forecasting technology generally gives us accurate predictions. Sometimes the forecasts are wrong. Sometimes the weather is just so damn changeable that all you can do is grit your teeth, take a mac or umbrella and just get on with it.

But what if the weather forecast was a matter of life and death … of the safety of 350,000 soldiers, sailors and airmen … and the future of the free world from Nazi domination?

Turn the clock back to the weekend of 2nd-4th June 1944 and try to imagine being in the (very big) boots of General “Ike” Eisenhower – and a less well-known Scottish scientist, Group Captain Dr James Stagg. Ike is the man who will say whether the D-Day landings should go ahead on Monday 5th June. Dr Stagg is the man who has to give a weather forecast that makes the launch of the massive expedition possible.

David Haig’s remarkable play Pressure, on stage at Yeovil’s Swan Theatre until Saturday 21st March, is the story of “the forecast that changed the course of history.” It’s a little-known story that sets the scene for probably the most famous invasion ever (after 1066 perhaps), a moment that turned the tide against Hitler’s army and began the inexorable process of driving the German forces back and bringing mainland Europe out from under the jackboot.

This is one of those intense dramas, with a handful of people in one anonymous room, the action spread over just a few days. The military leaders of Britain and the US are holed up in this unidentified location, overlooking the English Channel, waiting with increasing stress for Dr Stagg to give a forecast that will allow Gen Eisenhower (Robert Graydon) to order the go-ahead for the air and sea Allied Expeditionary Forces.

Dr Stagg (a powerful and involving performance from Ben Woof) is a taciturn Scot, whose attention is also being drawn to a hospital in Southampton where his wife is about to have their second baby – she had barely survived the birth of their first son and Stagg is desperate to know how she is.

But first, he has not only to interpret the flow of meteorological data coming in by telephone from across the Atlantic, from the Arctic regions and from Europe. He also has to counter the over-optimistic forecasts of the American weatherman, Col Irving Krick (Shaun Driver at his charismatic best). Krick’s methods – noticeably successful for American forces up to now – are based on historical precedents. He looks at the detailed reports of the same day from previous years, and uses them to frame his forecasts, so he is convinced that 5th June is going to be a fine and sunny day.

Stagg is drawing on years of observation that began as a young boy on a fishing boat off the west coast of Scotland. He is certain that the data and the Jet Stream (at that time still a controversial theory rather than a recognised climate feature) and other high altitude weather patterns indicate dangerously high winds and storms over the Channel on the fateful Monday.

Who will General Eisenhower believe? If he makes the wrong decision, the lives of 350,000 Allied servicemen will be massively at risk. Thousands could die at sea. The RAF might not be able to get the essential bombers in the air. Delay could allow the Nazi forces to be more prepared.

The story is compelling, and there is a gathering and utterly convincing ratcheting up of the emotions as the weather data keeps coming and tempers fray. As well as the three protagonists, the play has a fourth and critical character, the English officer, Lt Kay Summersby (Liz Stallard), the real life woman who was Eisenhower’s driver in the war and had a romantic relationship with him. With that clipped well-bred English voice that we know from wartime radio and film recordings, the actress captures the efficiency of the woman who ensures that there is always coffee, something to eat, that there is a listening ear for a man under extreme stress … while she knows that a successful D-Day landing and the end of the war will inevitably be a bitter personal loss and sorrow.

Robert Graydon, another, (with Driver and Woof), of Yeovil’s outstanding actors, inhabits Eisenhower with physical presence, a voice that can command instant action and obedience and a warmth and humanity that makes even the most unmilitary-minded in the audience understand why the men would have loved him. Graydon’s American accent is not always consistent, but that is unimportant in the power of his performance.

Like most of the audience, I didn’t know the play and I knew nothing of Dr Stagg, Col Krick or the significance of the weather forecast on 3rd June 1944. Director Mark Payne has brought the story vividly and compellingly to life, with his excellent cast and convincing characterisations of even the briefest appearances of the other senior officers.

In the end, the story hinges on a unique feature of this country and its people. As Dr Stagg tells Col Krick: “Nothing is predictable about the English weather. That’s why we love to talk about it.”

FAC