PRIME Minister Winston Churchill began to look upon an invasion of Europe as a serious option in the summer of 1941 - while most people were expecting the Germans to invade Britain.

In August 1942, 10,000 troops including 6,000 Canadians took part in Operation Jubilee to seize the heavily-defended Channel port of Dieppe, hold it for a few hours, then withdraw. The adventure ended in disaster, leaving 1,000 soldiers dead and 2,000 as prisoners of war.

Initial planning for Overlord - a codeword personally chosen by Churchill - began in March 1943 in the boardroom of a former bank in St James's Square, London.

Detailed planning began in January 1944 at Southwick House, a requistioned stately home near Portsmouth. It has remained in military hands ever since.

At the same time the Germans began to get wind that the Allies were planning an invasion. They even understood the operation was being called "Overlock".

To help Overlord planners build up information about the French coast, the BBC appealed for holiday snaps.

More than 30,000 arrived in the first post, and ten million over the next two years.

The French Resistance network provided 4,000 maps giving the locations of the German defensive positions in northern France.

Deception and camouflage unit R-Force built 500 rubber tanks, 50 dummy airfields, 400 cardboard soldiers and 500 rubber 25-pounder guns to create the impression that the Dover area was the invasion launch point.

Mulberry harbours were built bit by bit all over Britain by a 45,000-strong army of construction workers. But none knew what they were building. By the end of June 1944, the floating harbours had been used to land 875,000 men in Normandy.

The Pluto pipeline laid across the Channel was used to pump 210 million gallons of fuel to the Allied forces in France. After the war it was salvaged and used to make pipes for 50,000 houses.

To carry and protect the invasion force, 359 warships, 1,000 minesweepers, 4,000 landing craft, 805 merchant ships, 59 blockships and 300 small craft were assembled in ports along the south coast during 1944.

More than 11,000 aircraft and 7,000 ships were assigned to Overlord.

The US forces - described as "overpaid, oversexed and over here" - began arriving in Britain in early 1942 after Japan attacked Pearl harbour. As D-Day approached, the number totalled 1,500,000.

They brought with them 137,000 wheeled and semitracked vehicles, 4,200 tracked vehicles and 3,500 pieces of artillery.

They were even issued with vomit bags in case the Channel crossing was rough.

"Got any gum, chum?" was how most British youngsters greeted the American forces.

D-Day was originally scheduled for June 4/5 but postponed until June 6 because of stormy weather.

156,000 troops took part in the initial June 6 landings, and of these 10,000 were to become casualties.

Over the next two months more than 1.5 million men and 1.6 million tons of supplies were landed in France.

During this time, the Allies suffered 210,000 casualties, including almost 37,000 dead. The German dead totalled 65,000.