On Saturday Southsea Sub-Aqua Club will send divers down to take pictures and video footage of what they think are Centaur CS IV tanks.

And during the dive they will also try to work out the mystery of how they were lost, given there is no shipwreck nearby.

The tanks, assigned to the Royal Marines Armoured Support Group, lie eight miles off East Wittering, West Sussex.

They were part of an 80-strong contingent bound for France on D-Day but sank in mysterious circumstances.

The divers have good reason to think the tanks are Centaurs after pictures were taken during an earlier dive.

The photographs were taken to the Tank Museum in Dorset last month and the suspicions hardened into near certainty.

Alison Mayor, who is leading the diving team, said: 'It's a real puzzle how the tanks and bulldozers came to rest so far off shore when there is no shipwreck nearby.

'These war machines are of significant interest, and we hope to find clues to solve the mystery of how and when they sank.'

David Fletcher, historian at the Tank Museum, said: 'We are 95 per cent sure the tanks are Centaurs.

'When I first saw the photos they both looked like little sponges but it was a question of going through them more closely.'

Mr Fletcher added: 'They are very rare – there are only two, in France, that we know about.'

The rusting tanks lie with two bulldozers and a field gun, but no ship.

The bulldozers are believed to be armoured Caterpillar bulldozers, used by the 79th Armoured Division of the British Army – there are no known surviving bulldozers of this type.

The team of 12 divers will spend five days taking measurements, photographs and video. The divers have Ministry of Defence approval and the project has a grant from the British Sub-Aqua Jubilee Trust and support from Silent Planet in Portland, Dorset.