“Perhaps only in Britain could one succeed in writing a thriller about the weather,” observed David Haig who both wrote and stars in this little-known true story about D-Day.

The drama opens in the Portsmouth HQ of the Allied Expeditionary Forces on Friday, the second of June 1944. General Eisenhower is poised to launch his forces on June 5th. 350,000 lives are at stake and the decision whether or not to attack comes down to the weather forecast. Haig is the dour and intense Scottish meteorologist Dr James Stagg who is called on to predict the weather for the biggest seaborne invasion in history. He soon clashes with the larger than life, flashy American, Colonel Krick (Tim Beckmann) who advises General Eisenhower. Krick (something of a ‘celebrity’ weatherman who is proud of having predicted three rain-free days for the filming of Gone with the Wind) is gung-ho, confident that the fair weather won’t change. Stagg has grave doubts about whether the conditions will support the landings on June 5th. “I’m a scientist, not a gambler” he cries, exasperated. The tension builds in the midst of meteorological charts and conversations with General Eisenhower and naval and air force chiefs and support staff. And on a very personal level Stagg has to hold his nerve knowing that his wife is facing a difficult birth that he is forbidden to attend. Indeed, at one point, suffering from lack of sleep and fuelled by anxiety and coffee, he shakes uncontrollably. Passionate, dedicated, fearful, vulnerable - Haig mesmerises with a tour de force that is totally credible. He is supported by vivid performances from other members of the cast. Kay Summersby, Eisenhower’s driver (possibly also his lover) played by Laura Rogers is an appealing character, stoic, intelligent and resourceful. Malcolm Sinclair gives Eisenhower just the right degree of decisiveness, an essential quality in order to believe in him as a leader of men. With its masterly creation of a febrile atmosphere, Pressure is a docu-drama that is both gripping and affecting.

Pressure runs at the Park Theatre in Finsbury Park until April 28. Box Office 020 7870 6876.