The British, Americans and Canadians landed on the D-Day beaches and their flags were still fluttering in the breeze on the day we visited some 71 years later.

This time the flags flew together, on the mast of the French pleasure boat Pays-en-Bessin, taking us from its home port to Arromanches, 45 minutes along the coast and along Gold Beach, one of the two beaches taken by the British on June 6, 1944.

It was a beautiful clear day with only a slight swell, past the 200ft high granite and sandstone cliffs, a bit like Dorset, green and tumbling to the sea.

We chug past the lobster pots marked by black flags, the outside decks of the boat maybe two-thirds full, with everyone keenly anticipating the point of our round-tour trip, the remains of the Mulberry Harbour at Arromanches.

This one of a series of incredible stories of human resource and endeavour we were to hear on a two-day trip to the Normandy beaches. And one now made more vivid by the introduction of a new boat service allowing visitors to get up close to the remains of the Mulberry.

Essentially, it was an artificial harbour created by 132 tugs towing empty concrete chambers across the Channel, then filling them with water in depths of up to nine metres. Pontoons and floating roadways were then built, protected by the concrete perimeter and scuttled ships.

The yards that built them in Britain didn't know what they had built: the Germans who photographed them didn't know what they were for. And although the harbour was in use for only five months, 10,000 vehicles and 120,000 men were landed at Arromanches.

"Without the harbours, no Army commander would have taken the decision to invade," says Lt Col Alain Ferrand in his book Arromanches: History of a Harbour. "This was probably the greatest military engineering enterprise undertaken since the Persian armies crossed the Bosphurus in BC 480."

Today, the rusting bollards that were used to tow the boats across the Channel are still there, the seagulls sitting on top. The steel superstructures have long been plundered for scrap, the other blocks blown up or removed. Maybe a quarter remain of the 100 concrete barriers remain.

It is a fabulous story - and good news for next summer, the boat's owners promise an English commentary will be available as well.

Nothing was lost in translation the previous day however, when the two of us took a day out with Katrine Poullard, who grew up behind Sword Beach, the other British front, and who has run individual tours of the region for years.

More than 90 per cent of visitors to the Normandy beaches are American, she said. There are 18 cemeteries looked after by the Commonwealth Graves Commission (CGC) and 28 in total, including six for German soldiers.

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