Video report by ITV News Correspondent Paul Davies
A man has been jailed for stealing a logbook worth £10,000 from a widow of an RAF airman who was in the Dambusters squadron.
Alexander Bateman, 48, was sentenced for two years in prison after a five-day trial at Wood Green Crown Court.
The military historian lied repeatedly after he was asked to return the "important historical artefact" and refused to tell police what happened to the book.
The book, which belonged to the widow of Sergeant John Fraser, has never been found.
His widow, Doris Fraser, 92, had given the logbook to Mr Bateman after he contacted her in 1996 as part of his research into the airmen involved in the infamous squadron.
Sergeant Fraser's daughter, Shere Lowe, asked for the book to be returned in 2003 - but was sent an envelope that had been carefully cut open at the bottom.
He initially claimed the logbook was lost in the post but then told the family he had recovered it from the Post Office.
He then changed his story and said that the widow had given him the book as a gift and produced the forged Christmas card as proof.
Ms Lowe, who said her mother was "physically sick" when she realised the book was missing, flew over from Washington in the United States for the court hearing and slammed Mr Bateman for his "cruel charade".
All I have wanted out of this from day one is just to see my father's history, to be able to hold it in my hands and to be able to see it for the first time, and to share it with my children and my family. I had every reason at the start to believe that this man was a historian and wanted to uphold the legacy of the Dambusters. The action that followed - the deception and the cruel charade, the lies, it's had its weight on our family.
Judge John Dodd QC said: "I consider this to be a despicable offence involving, as it did, abusing the trust placed in you, presenting yourself as a genuine historian, by the widow of a war hero.
"You decided to keep the logbook, treating it as your own, misleading the family when they sought its return, which added to their sense of loss and betrayal."
Sgt Fraser, who was born in Canada, was a member of 617 Squadron.
His plane was shot down and he was held as a prisoner of war after being interrogated by the Germans.
After the war he moved to Canada with his wife, but died in 1962 in an air accident.