THE D-Day invasion would have failed without the mind-blowing innovation which enabled the Allied forces to be supplied with munitions as they pushed into France.

Can you imagine the first reaction to the suggestion that two giant harbours, each the size of Dover Harbour, should be towed across the Channel in sections and then put together, under hostile conditions, in France?

But that's exactly what happened. The largest self-assembly project in history, the Mulberry harbours, were to become one of the legends of D-Day.

These floating harbours were built in Britain and towed to France by about 150 tugs during Operation Overlord.

About 20,000 workers all over Britain constructed the sections some of the work was done on the banks of the Medway and Thames but most of the workers didn't know what they would be used for. The mission was that secret.

Constructed of hollow concrete blocks and unwanted merchant shipping filled with concrete and sunk, Mulberry harbours were Churchill's innovation that made the Operation Overlord campaign and D-Day landings possible.

These artificial harbours involved 600,000 tons of concrete, 33 jetties and 20 miles of floating roadways, that could be used until major ports could be captured and cleared for Allied use.

The first components for the first harbour, Mulberry A, arrived at Omaha beach in the American sector on D-Day itself, while Mulberry B arrived in the British-Canadian sector at Arromanches.

Within days, more than 30,000 troops, 25,000 tons of stores and hundreds of vehicles were being landed via these harbours.

Then calamity struck. The worst summer storms to strike Normandy for years destroyed Mulberry A, reducing the amount of manpower and munitions being landed to a mere fraction.

However, Mulberry B and smaller versions called Gooseberries went on supplying the invasion force.

Remnants of Mulberry B are still in evidence at Arromanches today. They remain as lasting memorials to Winston Churchill's insistence that he didn't want problems just solutions.