A German U-boat lost for more than 100 years has been uncovered on a seabed off the coast of East Anglia.

The submarine, named the SM U-31, left Germany on January 13 1915, never to return.

Engineers working on a wind farm project east of Norfolk and Suffolk unearthed the wreck about 90km offshore at a depth of about 30 metres.

The find was made by developer Scottish Power Renewables and its partner Vattenfall in 2012 but has only now been officially identified.

Mark Dunkley, marine archaeologist at Historic England, said: "SM U-31 was commissioned into the Imperial German Navy in September 1914.

"On January 13 1915, the U-31 slipped its mooring and sailed north-west from Wilhelmshaven for a routine patrol and disappeared. It is thought that U-31 had struck a mine off England's east coast and sank with the loss of its entire complement of four officers, 31 men.

"The discovery and identification of SM U-31 by ScottishPower Renewables and Vattenfall, lying some 91km east of Caister-on-Sea, Norfolk, is a significant achievement.

"After being on the seabed for over a century, the submarine appears to be in a remarkable condition with the conning tower present and the bows partially buried.

"Relatives and descendants of those lost in the U-31 may now take some comfort in knowing the final resting place of the crew and the discovery serves as a poignant reminder of all those lost at sea, on land and in the air during the First World War."

Dutch navy divers were originally called in to see if the wreck was one of their submarines missing since 1940.

Video footage highlighted clear images of the conning tower and deck layout, which suggested the wreck was German.

The wreck is 57.6 metres long, 4.1 metres wide and 4.6 metres high and the bow appears to be facing south.

Damage was found at the bow and the stern, so the original length could be slightly longer than it appears, as suggested by debris surrounding the wreck.

Charlie Jordan, ScottishPower Renewables' project director for the East Anglia ONE wind farm, said: "The scanning team were expecting to see wrecks, but such a discovery was quite a surprise and has been extremely interesting."

Andy Paine, Vattenfall project director of East Anglia Offshore Wind Farm, said the Receiver of the Wreck and other authorities had been informed.