After interviewing at least 50 British and American ex-servicemen and examining unpublished material in United States military archives, the London-based researchers tracked Eisenhower's headquarters down to a wood near Portsmouth, Hampshire, by conducting a search of previously unexamined aerial photographs taken at the time.
The discovery was made by a military historian, Winston Ramsey, editor of a Second World War history magazine called After The Battle.
Using a magnifying glass to carry out a close examination of the 50-year-old black-and-white air photos, Mr Ramsey succeeded in pinpointing the location of Eisenhower's personal headquarters in which he spent the period 2-12 June 1944. D-Day was 6 June. All that was known about the command post before was that it was a small tented encampment near Southwick, just to the north of Portsmouth.
Now, however, examination of a picture taken by the US Army Air Force on 21 April 1944 has for the first time revealed not only the location but also the complete layout of the complex. Although the command post was in a wood and the pictures were taken from 12,000ft, tents and vehicles became visible when the photos were massively enlarged. Full details of the discovery will be published next week in a special issue of Mr Ramsey's magazine After the Battle.
Researchers led by Mr Ramsey surveyed the site and recorded what meagre evidence - broken concrete, barbed wire - survives.
The team even found the spot where Eisenhower's tent had been. Records say it had a concrete floor - and indeed the team found fragments of concrete that had survived.
Because its location was previously unknown, much of the site - including the concrete floor beneath Eisenhower's tent - was destroyed or damaged when a tree plantation was set up there a few years ago.
The command post was the ultimate control centre for the invasion of Europe. It was to this wood that de Gaulle and Churchill came to discuss the invasion plans with Eisenhower.
The command post, hidden deep inside the wood, was code-named 'Sharpener'. It consisted of Eisenhower's personal office tent, his sleeping trailer, a mobile office and telephone switchboard, trailers with maps and teletype machines, tents for senior aides, a weather tent, and tents for guards and cooks.
From this wood, contact was maintained with Washington, with 10 Downing Street, and after 6 June with his commanders in Normandy. Sharpener camp was only 200 yards long and less than 70 yards wide.
Mr Ramsey has also found the location of the much larger D-Day 'forward' headquarters (one 'step' behind the Sharpener 'advanced' headquarters).
The new research shows that this larger complex - codenamed 'Shipmate' - was located just 300 yards south of Sharpener in an adjacent wood and had hundreds of tents and more than 1,000 staff.
It was in use from 1 July to 1 September 1944 when the forward headquarters was moved to France.
In the 14 months before D-Day, invasion planning HQ were set up first at Norfolk House, St James's Square, London; then at Bushy Park, Teddington, west London, and finally in the woods north of Portsmouth.
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