As a great port on the East of England, Dunwich was nothing short of a medieval metropolis. Eight churches, eighty ships, five religious orders - including the Benedictines, Dominicans and Franciscans - and prosperity to rival London from its trade in wool, grain, fish and furs. Such was the city’s prestige that, under Edward I, it was granted two seats in Parliament.

But that was before Dunwich was swallowed by the sea. This morning, more than five centuries after the last of a succession of storms and sea surges battered the Suffolk city into little more than a village, a research team will set sail to discover the secrets of a British Atlantis.

Using the latest acoustic imaging technology - designed to penetrate the high silt levels that have reduced visibility in the water at the site, a mile off the coast, to inches - the researchers hope to reveal Dunwich in its prime. For Stuart Bacon, a marine archaeologist who has spent 30 years studying how Dunwich disappeared, it will be a momentous day. Mr Bacon has explored the site by touch, using a map from 1587, on more than a thousand dives, but with limited success.

Now with a team from the University of Southampton, led by Professor David Sear, he hopes to locate and catalogue 16 large structures dating back to the 14th century, including at least two churches, a monastery and a palace. Professor Sear said that the team hoped, over the course of the next two days, to identify structures that could be correlated with ancient maps and documents.

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Planning for the £25,000 project has taken more than two years, backed by funding from English Heritage and the Esmée Fairbairn Foundation.

“We will be scanning the sea floor, going up and down in grids,” Professor Sear said. “We know from maps and documents that many structures existed, but we do not know where they were, and this will solve that puzzle.”

He added that the expedition did not expect to find any standing structures because most buildings had fallen from cliffs into the sea.

Dunwich had a prominent entry in the Domesday Book. By 1173 it was a place of such substance that Robert, Earl of Leicester, attempted to land 3,000 Flemish troops on its beaches in an attempt to depose Henry II and replace him with his son.

In 1205 there were five royal galleons in the city – a similar number to those in the Port of London – while in 1242, when the truce between King John and the French monarch broke down, Dunwich was able to muster 80 ships to go to the King’s aid.

The demise of Dunwich, perched 14 miles south of Lowestoft, gathered pace in 1286 when a huge surge hit the East Anglian coast. Within 50 years hundreds of houses and other larger buildings had been consigned to the shallow reaches of the North Sea.

Another fierce storm in 1328 destroyed the Benedictine cell, an offshoot of Ely Cathedral, and swept away the Franciscans’ Greyfriars priory and the Dominicans’ Black-friars priory. Two decades later a tempest swept 400 houses, two churches and various shops and windmills into the sea.

In 1510 a pier was erected as a breakwater when the sea approached the market place. The churchwardens at the cruciform church of St John the Baptist sold off all the plate to raise money to build another pier to deflect the waves from their church, but it, too, went over the cliffs in 1542.

And so it went on, until Suffolk was left with the Dunwich of today, a coastal village of shingle beaches, tourists and much local legend - including the sound of midnight tolls of church bells coming from beneath the waves.

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