The wreck of a royal warship which sank more than 340 years ago while carrying the future king James Stuart has been discovered off the east coast, in a find experts say is the most significant for a generation. The HMS Gloucester ran aground off the Norfolk coast on 6 May 1682, drowning up to 250 crew and passengers as it sank within an hour of hitting a sandbank. Since the 17th century the wreck has lain undiscovered - until it was found by two diving brothers from Norfolk after a four-year search over 5,000 nautical miles. They found the site - which lies 28 miles off Great Yarmouth - in 2007 but due to the time taken to confirm the identity of the ship and the need to protect an ‘at risk’ site, which lies in international waters, it is only now that its discovery can be made public.

It has been described by a historian as the most important maritime discovery since the Mary Rose, the warship from the Tudor navy of King Henry VIII.

The sinking of the Gloucester - and the huge loss of life it caused - came about because of a dispute between James, then the Duke of York, and the ship’s pilot James Ayres about navigating the treacherous Norfolk sandbanks.

James barely survived, having delayed abandoning ship until the last minute and needlessly costing the lives of many who, because of protocol, could not abandon the ship before royalty.

The future king accepted no responsibility for the sinking, instead blaming the pilot and wishing him to be hanged immediately, though Mr Ayres was in fact court-martialled and imprisoned.

James went on to reign as King James II of England and Ireland and James VII of Scotland from 1685 until 1688, when he was deposed by the Glorious Revolution.

The Gloucester represents an important potential turning point in British political history: a royal shipwreck causing the very near-death of the Catholic heir to the Protestant throne at a time of great political and religious tension.

The ship was commissioned in 1652, built at Limehouse in London, and launched in 1654.

In 1682 it was selected to carry James to Edinburgh to collect his heavily pregnant wife and their households - the aim being to bring them back to King Charles II’s court in London in time, it was hoped, for the birth of a legitimate male heir.

The ship set sail from Portsmouth, with James and his entourage joining it off Margate in Kent, having travelled by yacht from London, before it ran aground off the Norfolk coast.

Diarist and naval administrator Samuel Pepys, who witnessed events from another ship in the fleet, wrote his own account – describing the harrowing experience for victims and survivors, with some picked up “half dead” from the water.

As well as James, HMS Gloucester carried a number of prominent English and Scottish courtiers including John Churchill, later the 1st Duke of Marlborough.