The last thing John Dadd expected to find off the current-swept headland of Duart, in the Sound of Mull, was an historic shipwreck. He was in the area to train naval divers, and in an off-duty moment decided to try this likely spot for lobsters. What he came upon instead were six iron cannons, an anchor, and piles of stones which he recognised as ballast from an ancient ship. The wreck lay 10m deep, at the foot of an underwater cliff just to the east of Duart Point. Further search revealed a copper ships kettle, a crushed and broken pewter tankard, and an intact Bellarmine flagon, its grotesque facemask scowling at him through the centuries. It dated to around 1650.

John Dadd realised that he had made an important historical discovery and resolved to return one day and investigate it more thoroughly. That was in February 1979. But he was never able to do so. In 1991, worried that the site might be found and possibly plundered by others, he passed his information to Martin Dean of the Archaeological Diving Unit (ADU), based at St Andrews University. That summer the Units research vessel Xanadu, accompanied by John Dadd, went to Duart and the wreck was relocated.

The ADU confirmed the presence of a 17th century shipwreck, and noted that parts of the site seemed to be unstable. Timbers, including pieces of fine panelling, had begun to emerge from the sediments at the cliff base, and were already beginning to show signs of physical and biological decay. On the ADUs recommendation the site was designated as a protected wreck by Historic Scotland, the responsible agency.

But before the designation came into effect, the site was independently discovered by members of the Dumfries and Galloway Branch of the Scottish Sub-Aqua Club. When they came upon it in the early summer of 1992, the seabed was a cornucopia of displaced archaeological material. Much more timber was now exposed, and among it were pieces of carved decoration from the ships embellished stern - the head of a warrior in sharp relief, and the lower part of the badge of the heir apparent to the British throne, with its three ostrich feathers and Ich Dien motto.

There were other finds - a hoard of silver coins, too corroded for identification; the brass lock plate of a Scottish snaphaunce pistol; and an intact grindstone. With commendable public spirit the club members, after declaring their recoveries to the Receiver of Wreck, gave them to the National Museums of Scotland.

Something was clearly happening to displace this important but fragile archaeological material and, once displaced, it was at the mercy of the fierce currents which run across Duart Point. With special authority from the government departments involved, the ADU was diverted from its normal duties for a week so that it could survey, record and recover all the items judged to be under immediate threat.

The objects included more carvings - most dramatically that of a winged cherub whose face peered enigmatically out of the sea bed. Beside it lay a small wooden keg and a human arm-bone. Among the other items recovered were two lumps of concretion which, on being X-rayed, proved to contain an ornate sword hilt and the virtually intact mechanism of a pocket watch.

Meanwhile, Donald MacKinnon of the Dumfries and Galloway Club had been demonstrating his skill as a historical researcher. The archaeological evidence made it plain that the wreck had occurred about the middle of the 1 7th century. Was there a historical episode around this time which might explain it Donald found a likely answer in the archives. In 1653 Oliver Cromwell, exasperated by a revolt in favour of the exiled Charles II on the west coast of Scotland, sent a small task-force to crush it. Among the rebels were the Macleans of Duart, whose castle still towers majestically above the wreck site.

Six government ships commanded by Colonel Ralph Cobbett arrived off Duart in early September, bringing troops and siege artillery. But they found the castle empty - the Macleans had wisely fled to a more remote stronghold. As Cobbett and his men were pondering the situation, a violent storm sprang up, tearing into the anchored ships. What happened next is described in a contemporary report:

While our men staid in this Island the 13th instant there hapned a most violent storme, which continued for 16 or 18 hours together, in which wee lost a small Man of Warre called the Swan that came from Aire, the Martha and Margrett of Ipswich, wherein was all our remayning stores of ammunition and provision, only the great Guns and Morterpeeces were saved. But that which was most sad was the loss of the Speedwell of Lyn, where all the men that were in her, being 23 seamen and souldiers (except one) were drowned. The rest of the Men of Warre and others of the fleete were forced to cutt their Masts by the board, and yet hardly escaped: wee lost alsoe 2 of our shallopps; and all this in the sight of our Men att land, who saw their freinds drowning, and heard them crying for helpe, but could not save them.

It is not certain which of the three ships lies off Duart, but the most likely candidate is the Swan. This small warship had originally belonged to Charles I, but was captured by the Parliamentarians during the Civil War. It seems unlikely that in her new guise the ship would have gone on displaying emblems of the old regime such as the heir apparents badge - that would be akin to putting swastikas on a WWII Spitfire - but an intriguing possibility has emerged.

It is known that on Cromwells orders the royal arms were taken down and replaced by the Commonwealth ones in many churches, but they were seldom destroyed. The canny church authorities, mindful that revolution can be followed by counter-revolution, hid them carefully away. Their forethought was rewarded with the Restoration of 1660, when once again the old symbols became politically correct.

Might the same have happened aboard ships which had once belonged to the King We think it probably did, for not only would this explain why the hated Stewart emblems were still aboard the Swan when she sank, but it could also account for their survival on the wreck site. Wrapped and stowed safely in the hold, such objects would have stood a much better chance of burial and preservation than they would have done had they remained high up on the stern. Whatever the reason, this is the first time that carved ship embellishments have been found on a historic wreck in British waters.

Historic Scotland, though anxious to protect and manage the site, had neither the expertise nor the resources to do so, and the National Museums of Scotland, although eager to acquire, conserve, and display the wreck material, were not equipped to deal with the problems of recovering it. The ADU, responsible for monitoring all designated historic wrecks off Britain, could not devote further time to a single site, however important. But it was unthinkable that such a discovery should be abandoned to natural destruction.

Up to this point my own involvement in the project had been peripheral. Now I applied for, and was granted, a licence to survey the site and see what could be done to arrest further damage. The immediate priority was to monitor it through the winter of 1992-3, and, with help from the Dumfries and Galloway Club, and colleagues in the ADU, we somehow managed to mount six winter visits, usually in appalling weather. It was as well we did, for the erosion was continuing to expose fragile material, and had we not been on hand to consolidate it with gravel, much would have been lost.

Meanwhile, a campaign had been launched to raise funds so that serious survey and assessment work could get under way in 1993. With the help of the Russell Trust we were able to create an underwater archaeological research unit with a full complement of diving and archaeological equipment, a Land Rover, an inflatable workboat, and a field station at Duart. We have now completed three seasons on the site.

The first requirement was a full survey, and to do this properly demands a lot of bottom time. About 450 diver-hours have been devoted to generating a detailed 1:10 record of the wreck and its environs, controlled by the three-dimensional Web for Windows computer program originally developed by Nick Rule for the Mary Rose survey. In all, over 500 one-metre squares of seabed have been individually drawn to scale and superimposed on a master plan. Every feature with a dimension of 5cm or more has painstakingly been incorporated in the plan. Our detailed site map has been further enhanced by contours at 25cm intervals, a photo-mosaic of the core area, a metal detector survey, and a plot of the sites ecological zoning.

This information is important for understanding the environmental factors affecting the wreck, which not only helps with its archaeological interpretation, but also allows us to quantify and perhaps mitigate the processes of erosion. We have set up instrumentation to monitor the current regimes on the site, and carried out a number of scientific studies (including an investigation of corrosion characteristics on the iron guns and anchor, and experiments on biological and chemical degradation of various materials).

So far there has been no excavation, but we have recovered a few more items uncovered by erosion. Another carving has turned up (showing the harp and thistle emblems of Ireland and Scotland), which reinforces the identification of the wreck as the one-time royal warship Swan. Quite substantial parts of the vessel herself appear to have survived, held down by iron guns and ballast, or buried in the sediment. The most threatened areas have been given short-term protection against further erosion with sandbags, and it seems likely that some excavation will take place in 1996, perhaps continuing for another two or more seasons. Our investigations have confirmed that substantial parts of the site remain unstable, so an archaeologically-controlled recovery of what they contain is probably the only sensible option. A final decision will be made early this year.

The Dumfries and Galloway Sub-Aqua Clubs prompt and selfless surrender of recoveries to the National Museums played a key part in establishing the importance of the Duart wreck. Nor would the series of visits over the crucial winter of 1992-3 have been possible without their support.

Now we have established a wreck visitor scheme. Three open days were held last summer, during which divers were able to follow a trail round the site. Over 80 divers participated, and their enthusiastic feedback has been overwhelming. We want to continue this scheme so that groups and individuals can see what we are doing, and appreciate why it is necessary for sites such as this to be protected. Historic wrecks are, after all, a heritage which should be enjoyed by everyone.

  • Dr Colin Martin is a Reader in Maritime Studies at St Andrews University.