"For every man that died at Dieppe, ten were saved on D-Day."

Admiral Lord Mountbatten

The Allies faced a huge problem in planning an invasion of France - they needed a port. It was accepted during the planning for the D-day operation that it would be difficult to capture the German controlled harbours on the channel coast. Cherbourg, Dieppe and St. Malo were heavily fortified and defended; it would take far too long and be too costly to attempt to take them. Even when captured it was unlikely that they would be operational.

In August 1942 the Allies launched a disastrous raid on Dieppe and had learned a costly lesson. It was an experimental assault to see how a large-scale attack would fair. Two thirds of the force were killed or captured within hours and German forces were well prepared for the attack. It was clear that more sophisticated amphibious equipment was necessary and rapid support for the troops landing in Europe would be essential to consolidate any gains. A cunning solution was needed.

Whale pontoon with Spuds at each corner

The answer? The idea was conceived, possibly by Churchill himself, of building harbours in Britain and floating them over to France. This imaginative solution could take the enemy unawares, but would need extraordinary secrecy, planning and engineering skill. Two of these floating harbours were to be built under the codename 'Mulberry'.

The Mulberries were formed of over 600 components in all. The most significant parts were the hollow concrete breakwaters codenamed 'Phoenix Caissons' that could be sunk when they arrived in France to form the main body of the harbour. To this were added 'Bombardons' or steel floats 200ft long moored off the artificial harbours to break up incoming waves. With steel in short supply, old battle damaged vessels were to be scuttled alongside the harbour to bolster any shortages of Phoenix components, and were given the codename 'Gooseberries' or 'Corncobs'. Within each of the protected areas there were three floating piers, or 'Whales' connected to the shore by floating steel roadways. The Whales used adjustable legs called 'Spuds' anchored to the seabed, to enable them to work whatever the state of the tide. The floating roads were named 'Crocodiles'.

The bold idea had become a reality, but where was this secret work completed?

The international situation

The situation in Britain

Preparing for invasion

Mulberry Harbours

Building a secret port

Operation Overlord

On the beaches