Cromwell's sunken fleet with its £2bn treasure may, at last, be raised

A project to locate a sunken fleet of 60 Cromwellian ships loaded with treasure worth £2bn was launched yesterday.

For more than 350 years the gold and silver coins and plates have lain undetected, but not forgotten, at the bottom of the river Tay near Dundee.

Oliver Cromwell's enforcer, General George Monck, sacked Dundee in 1651, reducing the port to ashes, massacring its inhabitants and stealing the possessions of the local merchants.

The attack was part of a campaign to crush remaining royalist support in Aberdeen, Stirling and Dundee at the end of the 1642-51 civil wars.

Because the walled city was regarded as the most secure place in Scotland, many of the country's wealthy gentry, including the Viscount of Newburgh and the earls of Tweeddale and Buccleuch, had stored their most prized possessions there.

But few had bargained for the cunning of General Monck, the determination of his 7,000-strong Puritan army and the power of his cannon. Monck discovered, through a spy that he sent to infiltrate the defences, that the army within the city regularly got drunk in the morning – which offered an opportunity to attack. Monck overcame Dundee's defences with ease, and in the bloody aftermath up to 5,000 citizens were slaughtered as the victorious troops went on a rampage of rape, pillage and plunder.

But Monck was not so fortunate with the treacherous waters of the river Tay.

As Dundee burnt, Monck decided to take his loot to Leith on the first leg of its journey to England. He ordered his men to commandeer more than 60 ships from Dundee's harbour and loaded them with an estimated £2.5m worth of coins, plus tons of valuable trophies including ornamental plates made of precious metals, religious artefacts stolen from churches and monasteries around Scotland.

But as they set sail in September 1651 a storm blew across the Tay estuary. All 60 of the ships sank in heavy seas as, crowded together, they were driven into one of the river's notorious sandbanks. It is not known how many died in the disaster, although Monck survived.

The Firth of Tay is only 40ft deep, but the treasure has remained elusive to generations of hunters because the dangerous waters have foiled previous salvage attempts.

Now a Coventry-based diving firm, Subsea Explorer, is to join scientists from the University of St Andrews and Scottish Natural Heritage in an acoustic survey of the estuary, which could lead to the recovery of the sunken booty.

While the university and Scottish Natural Heritage are surveying the estuary with a view to designating it a special conservation area, the dive company is "piggy backing" in an attempt to find Monck's loot.

The treasure hunters plan to spend the next 10 weeks using stae-of-the-art acoustic equipment to map the river bed and locate the wrecks which, according to ancient maritime charts, are buried deep in sand about three miles south-east of Budden Ness.

Gary Allsop, the chief executive of Subsea Explorer, whose company has taken part in dives to the wreck of the Titanic, described the hunt as "one of the most exciting and sexiest jobs I've ever undertaken". He added: "It has everything: history, technology and the romance of buried treasure.

"We have the best technology and the best people behind us and I'm confident that if there is sizeable amounts of metal, for example gold and s ilver bullion down there, we will find it. If so, it will be of major historical and archaeological significance."