A 77-year mystery has been solved with the discovery of a Second World War landing craft – over 100 miles from where it was thought to have sunk.

Analysis of sonar data collected from a shipwreck off the North Wales coast has been identified as the Mk III Landing Craft Tank LCT 326, which was thought to have disappeared off the Isle of Man in 1943.

The vessel, which was built in Middlesbrough and launched in April 1942, was designed to land armoured vehicles during amphibious operations.

This type of highly specialised craft was used extensively during the D-Day operations of June 1944.

LCT 326 disappeared while transiting from Scotland to Devon in February 1943 with the loss of 14 crew.

The Admiralty listed the cause of the loss at the time to bad weather or collision with a mine off the Isle of Man.

New research by a team of marine scientists and technicians based at Bangor University now places the wreck over 100 miles away off Bardsey Island.

They worked with nautical archaeologist and historian Dr Innes McCartney, from Bournemouth University, to analyse multibeam sonar data collected by the Prince Madog research vessel.

“The wreck of LCT 326 is one of over 300 sites in Welsh waters which have been surveyed by the Prince Madog and the aim of this particular piece of research is to identify as many offshore wrecks in Welsh waters as possible and shed light on their respective maritime heritage,” said Dr McCartney.

“This aspect of the project has resulted in many new and exciting discoveries relating to both world wars, of which LCT 326 is just one example.”

Documents in the National Archives show the ship was part of the 7th LCT Flotilla and was on a transit cruise from Troon to Appledore.

The flotilla, under the watch of HMS Cotillion, set sail on January 31 1943 and according to records the weather was ‘heavy’ and the flotilla made slow progress south.

The flotilla passed the Isle of Man at daylight on February 1 and continued south. That evening as the weather freshened again, HMS Cotillion made a check on the flotilla and observed that LCT 326 was still with the convoy.

That was the last time LCT 326 was seen and the position at which this check was made was recorded as being just northwest of Bardsey Island.

The wreck has now been identified as being located in a position 25 miles further south from where LCT 326 was last seen and in near-perfect line with the flotilla’s course lying in over 90 metres of water.

The dimensions and appearance of the wreck from the sonar data show that it is 58 metres long and 10 metres wide, which is similar to the dimensions of a MKIII LCT.

The wreck is shown to be in two halves, lying on the seabed 130 metres apart.