Troops "sacrificed'' to protect the intelligence secret that helped win World War Two will get their own memorial next week.

The men, some from the North-East, were captured during the North African campaign and died on six Italian ships attacked by the Navy.

They included 50 soldiers of the Durham Light Infantry and 26 from the 4th Durham Survey Regiment of the Royal Artillery.

The SS Scillin and the Nino Bixio were attacked in the Mediterranean in 1942 as they sailed with their cargo of British prisoners.

The son of one of the 797 victims of the sinking of the SS Scillin has uncovered documents in the Public Records Office showing that naval top brass in the Mediterranean knew in advance that the ships were carrying POWs.

Brian Sims, of Lincolnshire, has spent years researching the "friendly fire'' tragedies and plans to write a book.

The retired pit deputy, whose father William, was in the Royal Signals Corps, says the men were killed to conceal the fact the British had cracked the complex codes used by Axis forces in their radio messages.

The Enigma code-breakers based at Bletchley Park, Bucks, were crucial to the Allied victory, giving vital information about the enemy's plans, but their work was a secret until the 1970s.

During the North African campaign highly sensitive intelligence, known as Ultra, was used to pinpoint the movement of ships carrying supplies to the German and Italian forces.

But they could not be attacked until there was some other plausible explanation for them being discovered - such as a reconnaissance plane spotting them.

The SS Scillin was sunk by the submarine HMS Sahib whose commander and crew, Mr Sims says, were unaware of the human cargo in its hold.

A tree planting and plaque unveiling will take place at the National Arboretum at Alrewas (correct), near Burton upon Trent, Staffs, on Tuesday (May13).

Mr Sims and another victim's son, Ron Graham, of Wilts, hope the relatives of some of the DLI men will attend the ceremony they have organised.

Mr Sims said: "The only logical answer for the sinkings was the protection of Ultra intelligence, no other answer is possible.

"Until 1992 when I found what had happened my father was still officially missing presumed dead while a POW even though the authorities knew.

"The plaque says that these men were sacrificed.''

Scillin survivor Tommy Marshall, of Birtley, Gateshead, a member of the Kings Own Regiment who died aged 79 in 1998, had his ashes scattered where the ship sank.