The turtle is being examined by scientists in Truro

It was spotted by a helicopter crew which was carrying out a survey for RNAS Culdrose.

The turtle, which is among the largest reptiles in the world, is thought to have been caught in lobster pot buoy ropes off Botallack, near Lands End.

It was towed to shore at Cape Cornwall by the Sennen Inshore Lifeboat where it took a team of volunteers to lift the 6ft (1.83m) beast.

They come over to gorge themselves on the jellyfish to bring themselves back to strength for the next breeding period, which is about every two to three years Peter Richardson, Marine Conservation Society

The leatherback has been taken to Truro to be examined by scientists.

Dave Jarvis, of the British Divers Marine Life Rescue team, was one of the team of volunteers who helped bring the turtle ashore.

He said: "We're not entirely sure it was killed in the fishing gear - it had obviously been dead for some time."

Peter Richardson from the Marine Conservation Society (MCS) said although leatherbacks are rare, July and August are the months they are most likely to be seen in UK waters.

Satellite tracking

He said: "There is an abundance of jellyfish here in August, on which the leatherback turtles feed.

"They come over to gorge themselves on the jellyfish to bring themselves back to strength for the next breeding period, which is about every two to three years."

The exact life expectancy of the leatherback is uncertain, but it is thought to be in excess of 50 years.

Earlier this month the Marine Turtle Research Group at the University of Exeter in Cornwall said it was mapping the progress of a leatherback turtle which had left an island in the Caribbean at the end of May after laying its eggs and could have been heading for Cornish waters.

But Brendan Godley from the group said their turtle, which is being tracked by satellite, is currently near Nova Scotia.