The mother of one of two Norfolk teachers murdered in France said prosecutors' decision to drop the investigation yesterday would finally give the family some peace.

The mother of one of two Norfolk teachers murdered in France said prosecutors' decision to drop the investigation yesterday would finally give the family some peace.

But the decision to close the file on the 1986 murders of Paul Bellion and Lorraine Glasby was criticised by the detective investigating the case, who said further work was essential.

Mr Bellion, 29, a craft and design teacher at Rosemary Musker High School, Thetford, and his 28-year-old fiancée Miss Glasby, a design technology teacher at Diss High School, were found in a maize field in Brittany in October 1986, a month after they had been shot.

The couple were found naked from the waist up, tied back-to-back and gagged, and both shot in the back of the neck.

They had gone off on a dream month-long cycling holiday a day after moving into their new home in Garboldisham, near Diss.

Despite a high-profile missing persons investigation, which included EDP reporters covering nearby villages in 'wanted' posters, and then a murder investigation, no progress was made and the case closed in 1991.

Then in August 2005 a dramatic confession by a prisoner to his cellmate led police to reopen the case and search a new DNA bank for possible leads.

Yesterday, however, justices admitted defeat, having failed to uncover any significant evidence other than the "purely intellectual" theory that the prisoner had killed the pair.

Detectives had argued that the unnamed prisoner killed the couple in a similar manner to murders committed in 1979, which his father was accused of.

He had done so to clear his father's name of the first murders - as his father was in prison in 1986 he could not have killed the Norfolk teachers, which would have cast doubt on the original convictions.

Hearing of plans to close the case, detective Pascal Huche said more investigation, including DNA tests, was essential.

But prosecutor Eric Bouillard said: "There is no evidence to support his theory, which is purely intellectual. The scenario is far-fetched and not supported by any evidence. Tens of thousands of euros have been spent on DNA tests; dozens of men have been deployed."

Talking to the EDP from her home in Merseyside yesterday, Elizabeth Bellion, 75, said she and husband Douglas had advised the prosecutor to drop the case.

"The investigation has just gone on and on," she said. "None of it can bring our son back. After 20 years of hurt and stress we now want some peace.

"That they haven't found anyone after all this time is hugely disappointing. I don't think the French investigators have done all they can - I know they think they're doing their job but they haven't even found the bikes.

"But we have to move on. The stress is still there, but after 20 years of hoping for answers, we now have to accept it's not going to happen and get on with our lives."