A diving company hopes it has struck gold in their search for a 17th century treasure trove which could be worth �2.5bn at today's prices.

Several sites have been identified in the Tay Estuary at Dundee where there are readings of precious metals under the sea bed.

A 15 inch diameter cannonball, believed to be 350 years old, has been discovered during the hunt for General Monck's treasure.

Coventry-based Subsea Explorer is using acoustic survey data commissioned by Scottish Natural Heritage (SNH) to search for General Monck's fleet, which sank in the Tay Estuary in 1651 after plundering Dundee.

The cannonball proves they are diving in the right area

Commanded by Cromwellian enforcer General George Monck, the fleet is reputed to have been carrying a cargo of 70 tonnes of plundered gold and silver when it sank in a violent storm.

The 60 ships were carrying gold and silver coins, plates and religious artefacts plundered from churches around Scotland.

Subsea chief executive Gary Allsop said the discovery of the cannonball proved his divers were working in the correct area.

Bond film

He was "101%" certain of finding gold somewhere in the search zone.

The cannonball was located by Jonathon Conte, who appeared as a diver in the James Bond film Tomorrow Never Dies.

Mr Allsop said: "Whilst walking with our underwater equipment Jonathon stubbed his toe on something - what we found was this."

Monck was Cromwell's (above) right-hand man

Subsea began its hunt early in July after scientists from St Andrews University were asked to carry out the research as part of SNH's consideration of whether or not to give the area "protected" status.

The equipment being used in the search includes a sophisticated metal detecting device capable of distinguishing precious from ferrous metals.

Several consents and approvals are needed before Subsea Explorer can start any more detailed investigative work.

This would include an assessment of any potential impacts arising from such work on the features of interest within the proposed Special Area of Conservation.