This is a dramatisation, with some historical tweaks, about the most important decision taken that ultimately became the turning point of WWII.
James Stagg (Andrew Scott), is a highly esteemed Met Office expert, recommended by Churchill himself, to become the Head of the Supreme Headquarters of the Allied Expeditionary Force Meteorological Committee. Leaving his heavily pregnant wife after a simple breakfast in their leafy suburban house, he is driven directly to SHAEF which is housed in what looks like a requisitioned stately home.
Arriving in his RAF Group Captain uniform, he's shown directly to the nerve centre of the forecasting team where amongst the 20 or so forecasters are dozens of historical weather charts for the same early June days throughout the previous forty years fill the walls. A cheery atmosphere is led by American meteorologist, USAAF Colonel Irving P. Krick (Chris Messina), who is holding court with jovial anecdotes of all the times he had forecast weather correctly for other WWII campaigns and Hollywood movie shoots in places that Stagg immediately realises are nowhere as volatile and dynamic as the North Atlantic.
Stagg then immediately mobilises the team to get on their phones and collate the latest meteorological data from as many relevant international weather stations as possible to obtain the best accurate up to date forecast. It's just four days before the proposed D-Day date and the first crucial weather report is due. Later, when it's time to present that crucial report to Supreme Allied Commander, General Dwight D. Eisenhower (Brendan Fraser), at the combined Chiefs of Staff meeting, Stagg pulls rank over Krick and because of their absolute disagreement on how to best forecast for the Normandy Landings, denies his request to attend the meeting too.
Stagg's initial report is that there is a good chance that major storms are on the way to the English Channel and the proposed day of invasion is totally out of the question. It doesn't help that the current weather is fine and clear. Obviously the joint chiefs of staff that include a very belligerent and condescending Field Marshal Montgomery (Damian Lewis) are all furious as they state that all the initial preparations are complete and all their various forces are ready to go.
Because of Krick's prior amicable and successful forecasting relationship with Eisenhower, Stagg initially feels isolated that his approach is not being listened to and when bad news comes on the phone about the bombing of a maternity hospital his wife was admitted to, right in the middle of an Eisenhower rant regarding the inconvenient report, he does not let on regarding his personal worry and defiantly stands his ground. Lieutenant Kay Summersby (Kerry Condon), the General's personal assistant is the only one who is empathic to the impossible stress James must be under and so becomes Stagg's ally.
This is a brilliantly told drama with, at it's core, a commanding and Oscar-worthy performance from Scott. All the supporting actors do very well too and Lewis is especially menacing as the overbearing Field Marshall.
The expansive detail of the Supreme Headquarters is a brilliantly recreated intense environment that gives the viewer a real insight into how the Allied War Machine must have been organised and what incredible responsibility certain individuals had. Also well-inserted archive footage of Allied troop organisations on the English South coast spliced in with newly shot scenes really did enhance the understanding of just what an incredible offensive preparation it all must have been. Of course, we all know the eventual outcome of Operation Overlord but seeing this important piece of history that led up to that decision of when to go, really puts in clear perspective the ultimate command Nature has on us mere mortals.













