An unearthed royal letter reveals how the Queen 's father conducted an affair with a married woman.
Edward VIII, who famously abdicated the throne in 1936, lured Lady Sheila Loughborough's husband away so his brother George VI could be alone with her.
The then Prince of Wales convinced Lord Loughborough to play a round of golf with him as a favour to his sibling, who was affectionately known as 'Bertie'.
The bombshell letter, written on June 9, 1919, has come to light after its owner put the missive up for auction.
Edward extended his devious golf invitation when he visited Lord Loughborough's home, Lankhills, near Winchester, Hampshire, with his brother in 1919.
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Bertie was said to have been infatuated with Australian socialite Lady Loughborough, although the future monarch's father King George V later warned him off seeing her.
In Edward's letter to his married lover Freda Dudley Ward, he wrote: "I simply couldn't hit a ball at golf & Bertie beat my head off, f- him... we motored on to Winchester reaching Lankhills at 5:30.
"After tea I managed to lure Loughie (Lord Loughborough) away on the pretext of wanting to play a few more holes of golf on the local course, so as to give Sheilie a chance of being alone with Bertie; they said they were tired & we left them..."
According to Mail Online, Simon Luterbacher, specialist at Forum Auctions, said: "A bit of sibling solidarity was at play as they tried to get George alone with Lady Loughborough.
"It was a bit conniving on their part, and it is unusual to find a letter which goes into such personal detail.
"The brothers clearly had a strong bond at the time, but this would change in later years with the abdication."
The letter is up for £2,500 at London-based Forum Auctions, with the sale taking place on February 10.
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George VI, who was in his early 20s at the time of the letter, met Lady Loughborough at a dance in Stafford House, London, in 1918.
Their affair lasted until George V reportedly found out about it in 1920 and offered to make his son the Duke of York if he dropped Lady Loughborough.
Later that year she returned to Australia in a bid to save her marriage, although the pair continued to correspond via letter and remained friends.
Shortly afterwards George VI met Elizabeth Bowes-Lyon - known to modern generartions as the Queen Mother - and they married in 1923, while his brother left Freda in 1934 and met American divorcee Wallis Simpson.
George VI had two daughters with his wife - the Queen, then known as Princess Elizabeth, and Princess Margaret.
The Queen Mother sadly died in March 2002 aged 101.
