Oil has always seeped from the wreck in small quantities, but two years ago it began to be washed ashore, raising an agonising dilemma: the obvious way to avoid environmental disaster was to slice open the hull and draw out the oil, but that would have meant violating the sanctity of the grave. Last week, however, a pioneering operation aimed at satisfying environmental fears and preserving the grave began smoothly, concluding a two-year search for a way to drain off the estimated 2,000 gallons of oil the Royal Oak took to the bottom on the night of 14 October 1939.
The vessel was torpedoed at her moorings by a U-boat which sneaked through a blockade at the entrance to Scapa Flow, a key wartime naval base. She sank in just 15 minutes. To this day the ship is still honoured with an annual remembrance service.
The site is a haven for wildlife. More than 8,000 grey and common seals swim around Orkney, while puffins and many waders flock to the islands in their thousands. Leakage from the Royal Oak and other vessels on the sea-bed has left a thin, shiny film of surface oil on the waters of Scapa Flow.
The Navy has spent the past two years exploring ways to avoid cutting open the wreck, with naval engineers working on a three-dimensional computer model of the ship based on the original plans at the Royal Naval Museum at Greenwich. "The fact that the ship is a war grave is one of the most important points we had to consider," said Steve Willmot, an RN press officer based at Faslane.
"The Royal Oak was the first major naval casualty of the Second World War and involved an immense loss of life. It wasn't just a question of sending divers down to the wreck, drilling a few holes and pumping off what came out. We had to maintain the integrity of the war grave. Everything we've done is with the approval of the Royal Oak Survivors Association and families of the dead."
Experts from the Ministry of Defence's Naval Support Command manufactured a metal umbrella-shaped canopy, secured to the upturned hull of the wreck with cables, siphoning off the oil which is leaking at a rate of a gallon an hour.
The canopy was lowered into place last week and the first gallons of oil have been collected in what the Navy described as a successful operation. The canopy will be drained each month in a process expected to last 15 years, though the Navy is exploring ways of accelerating the drainage.
Orkney has strong naval links stemming from the two world wars. In 1919 the German High Seas fleet of 71 ships was scuttled in Scapa Flow and many British ships guarding the entrance were also holed. Many Orcadians felt strongly that the Royal Oak should not be tampered with but, conscious of the Braer tanker disaster which spilled 84,500 tonnes of crude oil off Shetland in 1993, they were also keen for the leak to be tackled as quickly as possible.
Environmentalists have expressed concern at the slow process of the solution, and would prefer the oil to be drained off swiftly rather than allowing a potential disaster to linger on for 15 years. Ross Flett of Orkney Seal Rescue said: "Scapa Flow is an important area for seals, and while the oil is down there, there is a possibility it could leak from other parts of the ship."
However, David Flanagan, a spokesman for Orkney Islands Council, thought the best solution had been found. "There has been mixed opinion but we're pleased with the way this has been handled. In some ways I think local people see the sheen of oil as a memorial to the dead of the ship and as long as that sheen doesn't cause any environmental problems they won't mind," he said.