In December last year, the last surviving D-Day veteran of my old regiment, the 13th/18th Royal Hussars, died peacefully in his care home. On 6 June 1944, 20-year-old Trooper Lawrence Burn had been the gunner in a specially adapted Sherman tank which, along with others of the regiment, had driven down the ramps of their landing craft 5,000 yards off Sword Beach and swum for almost an hour through the high swell to land a few minutes ahead of the assaulting infantry in order to suppress the defenders’ fire. Years later, Burn was still in awe of the scale and execution of the Normandy landings: ‘I don’t know who planned it – a committee, I suppose,’ he told a journalist on his 90th birthday, ‘but it was wonderfully, wonderfully done.’

The man with the greatest claim to having been master planner was Lieutenant-General Frederick Morgan. In March 1943 he was appointed to the post of Chief of Staff to the Supreme Allied Commander (COSSAC), no actual Supreme Allied Commander being appointed until December – Dwight Eisenhower. Morgan, with a small Anglo-American staff, worked methodically through the problems and options, choosing Normandy rather than the Pas de Calais for the assault. Eisenhower, on taking command, accepted the general concept, but wanted to land five divisions simultaneously rather than Morgan’s three with two in reserve. Morgan agreed it was better, but he’d had to work with the numbers given him. Montgomery, whom Eisenhower accepted somewhat uncertainly as his landing force commander, agreed that five divisions were essential; and so the extra two were inserted. This at once increased the strain on the naval side of Operation Overlord (code name for the Normandy landings preparatory to subsequent operations for the liberation of Western Europe) – Operation Neptune.

Fortunately, Monty’s naval counterpart, the Commander-in-Chief of the Allied Naval Expeditionary Force, was Admiral Sir Bertram Ramsay. Churchill, as First Lord of the Admiralty, had brought him out of retirement in 1939 to be C-in-C Dover. It was Ramsay who masterminded the Dunkirk evacuation the following year. He had then played a major role in planning and commanding the landings in North Africa and Sicily in 1943 before being brought back to England for Overlord in October that year.

Ramsay was ultimately responsible for what the historian Correlli Barnett (not one to place laurels on a head if a crown of thorns would do) called a ‘never surpassed masterpiece of planning’. But it is easily overlooked when attention is drawn to the fighting on the beaches and beyond. Ramsay himself, writing at the end of July 1944, said that because Neptune ‘went so smoothly, it may seem to some people that it was all easy and plain sailing. Nothing could be more wrong. It was excellent planning and execution.’

Neptune was an operation of three parts: the assembly of the great Allied armada; the putting ashore of the five Allied assault divisions on D-Day to secure a bridgehead, and those which followed throughout June; and their logistic support throughout the fighting in France. All of this Nick Hewitt, formerly head of research and collections at the National Museum of the Royal Navy, relates assuredly, although there is the odd infelicity that will jar with naval professionals, such as describing the commander of a German torpedo-boat flotilla, a korvettenkapitän (lieutenant-commander equivalent in the Royal Navy), being aboard his ‘flagship’ rather than his ‘flotilla leader’.

The author also wants Neptune to be called the ‘Battle of the Seine Bay’. This is unlikely to catch on, especially after 80 years. Besides not having the ring of Aboukir Bay or Quiberon Bay – or even Sole Bay – a battle really ought to involve hard fighting against the enemy, something that Neptune lacked. By Hewitt’s own account, German naval forces in the Seine Bay were ‘catastrophically outnumbered’. On D-Day itself, mines and fire from shore batteries did the most damage to ships and landing craft, though a faltering attack by torpedo boats sank a Norwegian destroyer. The Royal Navy lost just 24 warships throughout the entire invasion effort, testament to both sea and air supremacy – and to seamanship. The weather was the greater enemy at times to the operation.

Indeed, Ramsay’s ultimate contribution to Overlord was his advice to Eisenhower when the landings, scheduled originally for 5 June, were postponed for 24 hours because of the weather. Eisenhower is rightly credited with the decision to go on 6 June, even though, when he took the decision, a gale was still blowing; but it was Ramsay’s advice that was the clincher. The forecast for the 6th wasn’t propitious: gusts of force 6-7 in the Channel, with winds a steady force4-5. Force 4 was enough to swamp the landing craft; but Ramsay said he was prepared to accept 4-5 as marginal with the possibility of the occasional 4-6. So they went.

He would receive no post-war honours, however, for on 2 January 1945 he was killed when his plane crashed on take-off outside Paris. His air counterpart on Overlord, Trafford Leigh-Mallory, had been killed in November when his aircraft crashed in the French Alps.

This is a very fine book – detailed, measured, comprehensive and vigorous. But the publishers do the author no favours by the endorsement on the cover: ‘Hewitt has achieved the impossible. He has retold the story of D-Day in a way that transforms our understanding.’ Besides the clichéd hyperbole, no one with the remotest knowledge of D-Day could be in any doubt about the sailors’ part in it. Trooper Burn certainly wasn’t.