Of the up to 1,000 vessels, from military warships to fishing boats, lifeboats and pleasure craft, that scrambled to help the stranded men, hundreds were sunk during the nine-day Operation Dynamo with the loss of many lives.

More than eight decades later, French and British archaeologists are embarking on a joint survey of the waters off the northern French town, using the latest technology to scour the seabed for shipwrecks from the heroic rescue armada.

They hope to learn more about 37 wrecks whose locations are known in the vicinity, and to locate other sunken ships – the exact whereabouts of which are unknown.

The project, jointly run by France’s department of underwater archaeological research (Drassm) and Historic England, will begin next week with a surface-level scan of the seabed, using geophysical survey equipment including a multibeam echosounder, side-scan sonar and magnetometer.