n Oxford maritime archaeologist has helped recover a unique relic of Nazi Germany's Second World War fleet from its watery grave.

Mensun Bound, 54, battled deep water, strong currents and the threat of pirates to unearth a huge bronze eagle standing on a swastika from the hull of the German pocket battleship, Admiral Graf Spee.

Yesterday Mr Bound, a Triton fellow in maritime archaeology at St Peter's College, said it was believed to be the only surviving example of the chilling emblems.

The pocket battleship was scuttled in 1939 in the mouth of the River Plate, between Uruguay and Argentina, but the eagle was found still attached to the hull last December during a dive on the wreck.

Mr Bound, who has already recovered valuable artefacts from the warship, was on the first plane out to investigate.

"It has been an exciting, but very tense operation," said Mr Bound, who lives in Horspath. "The recovery was dubbed Operation Big Bird and was carried out under extreme secrecy. "The Uruguayan Navy was concerned it would be stolen, but we were also extremely worried about how people would respond to the find. Quite apart from the power of this symbol to offend, it could also attract unwanted attention from neo-Nazi groups.

"The swastika is the quintessential symbol of evil. No other can match it for emotive power or for the sheer hideousness of its message."

Mr Bound and the other archaeologists worked in extreme conditions to release the eagle from its watery grave.

He explained: "It was buried deep in mud. The currents were ripping at us, the water was pitch black and with 145 bolts holding it on to the ship, we were lucky if we released six in a day." The Admiral Graf Spee was scuttled in the River Plate, off Montevideo, on December 17, 1939, four days after a fierce battle in the South Atlantic with the British cruisers Hms Exeter and HMS Ajax and the New Zealand ship HMNZS Achilles.

Mr Bound said: "The spread wing eagle, which is over two metres high, curved around the vessel's stern.

"Other German capital ships sported the national bird across their sterns, but this is the only one to have survived -- it is a unique find and in that respect is priceless.

"At the moment there's so much excitement here in Uruguay about the discovery, and people are saying it could be sold for up to £26m.

"I would like to see it go to the maritime museum of Montevideo, to be displayed with the other artefacts in the Battle of the River Plate exhibition."