British historian Andrew Lownie has claimed that the late Lord Mountbatten and his wife Edwina spent their married lives engaging in a stream of affairs.

In his new biography The Mountbattens: Their Lives and Loves, the author told how the last viceroy of India, who was assassinated in 1979 by an IRA bomb aged 79, was initially devastated by wife Edwina's affairs.

The late Edwina, who was hailed as 'England's most beautiful woman' at the time she married Louis, the uncle of Prince Philip, was described as 'sex obsessed', and reportedly embarked on as many as 18 affairs - including Indian Prime Minister Nehru and singer Leslie 'Hutch' Hutchinson.

According to the book, Lord Louis Mountbatten - who was said to be 'more awkward in the bedroom' - agreed to an open marriage with Edwina, before embarking on his own affairs - allegedly with both women and 'young' men.

British historian Andrew Lownie has claimed that the late Lord Mountbatten and his wife Edwina spent their married lives engaging in a stream of affairs. They are pictured in their earlier days

Lord Mountbatten was said to have even admitted at one time: 'Edwina and I spent all our married lives getting into other people's beds.

According to the biography, the British Royal Navy officer once wrote to her: 'I wish I knew how to flirt with other women, and especially with my wife.

'I wish I had sown many more wild oats in my youth, and could excite you more than I fear I do'.

Edwina's alleged taste for affairs following their wedding in 1922 reportedly began with army officer Hugh Molyneux, before was said to move on to millionaire heir Stephen Sandford.

But the troubles only really started when her active social life began to appear in the press, and she was named in a divorce petition from the wife of Louis' naval colleague Henry Simpson - alleging they had committed adultery.

Edwina's alleged taste for affairs following their wedding in 1922 (pictured) reportedly began with army officer Hugh Molyneux, before was said to move on to millionaire heir Stephen Sandford

Lord Mountbatten was said to have finally confronted her, and after an emotional showdown the couple reportedly agreed on an open marriage - as divorce was too much of a shame in the 1930s.

Edwina's more controversial alleged affairs included Indian prime minister at the time Jawaharlal Nehru, and West End actor Paul Robeson - which caused much scandal as interracial relationships were frowned on at the time - resulting in Buckingham Palace suing The People paper at the time.

Elsewhere there were whispers of a tryst with entertainer Leslie Hutchinson - with her alleged affairs reportedly often staying in her marital home.

Edwina's daughter Pamela Hicks once revealed of their Broom House family home in Park Lane: 'When my mother returned from shopping one day she was met with, 'Mr Larry Gray is in the drawing room, Mr Sandford is in the library, Mr Ted Phillips is in the boudoir, Señor Portago [is] in the anteroom and I don't know what to do with Mr Molyneux'.

Edwina's more controversial alleged affairs included Indian prime minister at the time Jawaharlal Nehru. They are pictured at a Reception Given By The Indian High Commissioner

West-Indian cabaret pianist Leslie Hutchinson (1900 - 1969), seen in 1954, was rumoured to be one of Edwina's companions

The late Edwina, who was hailed as 'England's most beautiful woman' at the time she married Louis, the uncle of Prince Philip, was described as 'sex obsessed', and reportedly embarked on as many as 18 affairs. Pictured: Lord Louis Mountbatten , kingGeorge's cousin , with his fiancee Edwina Ashley on liner Majestic arriving in New York april 10, 1922

Edwina died in her sleep of unknown causes at the age 59 of 1960.

And the biography reports that Louis Mountbatten soon began his own affairs, his first said to have started in 1932 with a married woman in her twenties, Yola Letellier, which reportedly lasted until his death.

Mountbatten was also said to be a client of French brothel keeper Madame Claude, and reportedly used her services while 'circling the air in a private jet'.

However 75-year-old FBI documents were obtained through a freedom of information request by British historian Andrew claim there was a darker side to his affairs.

Agents began compiling the file, which spans more than three decades, in February 1944, shortly after Mountbatten became supreme allied commander of southeast Asia.

The intelligence files describe the 1st Earl Mountbatten of Burma and his wife Edwina (pictured in their younger days) as 'persons of extremely low morals' who frequently had extramarital affairs

Prince Charles' uncle and valued mentor Lord Mountbatten (pictured together) was a 'homosexual with a perversion for young boys', according to a secret dossier compiled by the FBI

Following his appointment, the FBI interviewed Elizabeth de la Poer Beresford, Baroness Decies, about another matter, and she brought up Mountbatten.

The file read: 'She states that in these circles Lord Louis Mountbatten and his wife are considered persons of extremely low morals.

'She stated that Lord Louis Mountbatten was known to be a homosexual with a perversion for young boys'.

Lownie's new book, to be published on Thursday, contains an interview with Anthony Daly, a rent boy to the rich and famous during the 1970s.

Daly claims: 'Tom said Mountbatten had something of a fetish for uniforms — handsome young men in military uniforms (with high boots) and beautiful boys in school uniform.'