AIR historian John Yarker is trying to solve the mystery of a Second World War bomber which was 150 miles off course when it crashed on a North-East hilltop, killing its crew of three.

The Blenheim aircraft was returning from a raid on Germany when it came down in flames north of Eggleston, near Barnard Castle, County Durham, a minute before midnight on November 26, 1940.

It is the latest tragedy to be investigated by Mr Yarker, a former RAF engineer and retired prison officer, who has researched 39 air crashes in the Teesdale area.

His theory is that the plane's radio, its only means of navigation, was damaged by enemy flak. This caused it to go astray on the way home and it was then hit by British defence guns.

Mr Yarker said: "It probably came in over the Tees rather than Norfolk, so it was understandable that our guns should attack it.

"It may then have followed the Tees past Darlington and Barnard Castle looking for a place to land."

The aircraft was seen in flames over Newbiggin, in upper Teesdale, before turning back. It came down a few minutes later. There was little formal investigation at the time.

Mr Yarker has sifted through Ministry of Defence records and discovered the plane took off that night from RAF Bodney, Norfolk. The pilot was Sergeant HK Collinge. There were two other sergeants on board - navigator and bomb aimer DG Osborne and wireless operator and gunner A Moore. The eldest was 22.

Their aircraft, Blenheim Mark 4 No R3914, took off with seven others and joined up with eight from RAF Scampton, Lincolnshire. Their raid on Cologne, in northern Germany, was a success and all 16 turned for home.

The other 15 landed at their bases safely. But the ill-fated bomber sent its last radio signal at 8pm.

Mr Yarker, of Cleveland Road, Barnard Castle, said: "It would still be over Germany at that time.

"I feel its radio must have been damaged just after that, which would explain why it went so far astray."

He has recovered parts of the aircraft, including the main throttles and a panel of fuselage, as well as a flying helmet, from the crash site, but is keeping the exact location a secret to foil souvenir hunters.

"The plane was on fire but it was not a massive blaze as the parts I've found are not burnt," he said. "This indicates that it was just about out of fuel when it crashed."

Asked why he spends time on such investigations, he said: "We owe it to the crews to try to find out what happened. Imagine these three young men in a crippled aircraft - lost, cold, and probably being fired at by their own side. They must have been terrified.

"I may not be able to solve this one but I'll keep trying. It is possible that another piece of evidence will turn up from somewhere and fit into the picture."

Mr Yarker, who is the mayor of Barnard Castle, is registered with the Ministry of Defence as an aviation archaeologist. This allows him to carry out research on crash sites. He has recovered pieces from other sites and given many of them to air museums.