Every month or so I meet up with my pal the Squire of Sidcup and we do lunch and browse bookshops (as you do.) To shake up the routine this time we went to see a matinee of David Haig’s play Pressure at the Ambassadors Theatre; the Squire observed that he was the youngest person there by several decades. It was my first visit to this charming, dinky little theatre in fourteen years, and it’s great to see it surviving so well. Now see here, Cameron Mackintosh, it’s bad enough you wanting to rename it the Sondheim when its current, age-old name is classy and distinctive as it is; but proposing to knock it down and rebuild it would show an atrocious disrespect for its heritage. In its 105 year history, this Grade II listed building has seen Vivien Leigh take her first West End steps as well as 22 years of The Mousetrap, 11 years of Stomp and countless other great productions – including one of my first dates with (as then) Miss Duncansby as I showed her a good time by taking her to see Dinsdale Landen and Liza Goddard in Wife Begins At Forty, 33 years ago. In the words of Harry Enfield, Oi, Cameron, No!

I digress, as I so often do. Pressure is based on the true story of how Group Captain James Stagg, Meteorologist with the Royal Air Force, persuaded General Dwight D Eisenhower to postpone the date of Operation Overlord – or D-Day as we usually think of it – because of the adverse weather he had predicted for the original date of 5th June 1944. This flew in the face of the advice of Colonel Irving Krick, the American meteorologist in whom Eisenhower usually trusted, who insisted that the weather conditions on 5th June would be perfect. As you can imagine, to say there was a lot riding on this operation would be something of an understatement; not only the safety of the thousands of men involved, but also the long-term benefits gained from a successful invasion of Europe. So it was vital to get the timing right. No wonder the play reveals that Stagg, Eisenhower and Krick had a rather tetchy working relationship.

This may sound like a rather unlikely topic for a play; and indeed you might wonder whether or not it can hold your attention for a full two-and-a-half hours, including interval. The answer is that yes, it can, just… The timespan of the play covers the stressful weekend from Friday 2nd to Tuesday 6th June, broken down into ten scenes – three in Act One and seven in Act Two. The first couple of days are spent arguing the rights and wrongs of the weather map and coming to the tense conclusion that the 6th would be better than the 5th; once the decision has been made, it only remains to see if it was indeed the correct decision, or if Stagg was wrong. As a result, the more significant “action” of the play – such as it is – all comes in the first couple of days; the remaining three or four scenes are all “sit and wait”.

To fill the waiting time, and to keep our interest up, David Haig turns our attention to the personal relationships between Eisenhower, Stagg and Kay Summersby, who was Eisenhower’s chauffeur and P.A. – and maybe a little more. There’s also a side story concerning Stagg’s wife going into labour, expecting their second child. Stagg is the embodiment of stiff-upper-lip, but nevertheless you can still see the additional nervousness caused by the worry about his wife and child. For me personally, I found the side conversations that revealed the personal issues beneath the surface were more interesting than discussions about isobars.

However, it did make you think how labour-intensive, and downright slow, the whole weather-forecasting phenomenon was in those days. Today you just click an app and you can see weather fronts skedaddling over whichever piece of land you choose, with the ability to customise the symbols and the degrees whichever way you want. In 1944 people had to create a physical wall chart, with all the barometric lines carefully hand-drawn over a basic map, assembled in response to notifications from individual weather stations that had been telephoned in. It’s a fascinating example of technological progress that we take completely for granted.

A relatively large cast for a relatively small stage gives a convincing impression of a busy, military office, with messages constantly being refreshed by lower-ranked personnel, and regular meetings with the Armed Forces hobnobs – not only Eisenhower, but also Carl Andrew Spaatz (Commander of Strategic Air Forces in Europe), Admiral Sir Bertram Ramsay, and Air Chief Marshal Sir Trafford Leigh-Mallory, who, a few months later would become the highest ranking officer to be killed in the war, when his aircraft crashed in the French Alps on the way to Ceylon to take up the post of Air Commander-in-Chief South East Asia Command. Such assembled seniority emphasises even more the importance of the work at hand.

David Haig takes the role of Stagg in his own play, and its an excellent portrayal of a focussed, intelligent, selfless individual compelled to hold his own in the face of enormous pressure (see what I did there) to cave in. He adopts a slightly surly Scottish accent – Stagg was born in Dalkeith – and his no-nonsense and no-sentiment approach to his life and work is very believable. His wiry nervousness is an excellent contrast to Malcolm Sinclair’s naturally relaxed but extremely powerful performance as Eisenhower, the kind of man who simply exudes authority and rarely has to raise his voice to get what he wants – but when he does, you really stand to attention. Making up the office triumvirate, Laura Rogers is excellent as Kay Summersby, on one hand insisting on conversational niceties like please and thank you, on the other, prepared to drive hours out of her way just to allay Stagg’s fears about his wife. The final exchange between her and Eisenhower was probably the best individual thirty seconds in the entire play.

There’s also great support from the rest of the cast, especially the smarmy personality of Krick conveyed very effectively by Philip Cairns and the willing helpfulness of gopher Flight-Lieutenant Andrew Carter played by Bert Seymour. Pressure has already enjoyed a revival UK tour – it originally saw light of day back in 2014 – and its run at the Ambassadors is scheduled through to the 1st September. An unusual, well-structured and detailed play that considers a vital, but frequently overlooked weekend during the war. I’d be lying if I said I was riveted by it, but it certainly makes you think!