"I am not going to see him during this time but in October I shall be returning to London, and he will then be taking his annual leave – I do certainly hope to see him while he is there...  "But it is only by seeing him in this way that I feel I can properly decide whether I can marry him or not.  "At the end of October or early November I very much hope to be in a position to tell you and the other Commonwealth Prime Ministers what I intend to do.  "The Queen of course knows I am writing to you about this, but of course no one else does, and as everything is so uncertain I know you will regard it certainly as a confidence."  Christopher Warwick, a close friend of Princess Margaret and her official biographer, said the letter was "a very remarkable and significant historical document which puts a completely different complexion on the accepted version of events".  He said: "This letter rewrites history, because here you've got a very determined and confident young woman in control of the situation, telling the Prime Minister that she has not decided and is wavering, which is at odds with what the public was led to believe and certainly with what she told me.  "The perception was that she gave up the love of her life for duty and protocol, but this letter sets a question mark over that. It shows that the love, conceivably, was not as strong as it was to begin with. It's likely she didn't want anyone other than Eden to know she'd had doubts, because it had gone so far."  Mr Warwick said that the letter also cast doubt on the long-held assumption that Princess Margaret believed she would have to renounce all her royal privileges if she married Townsend. In fact, Eden, Britain's first divorced prime minister, who replaced Winston Churchill in April 1955, had ensured she would keep her HRH title and a civil list allowance.  Mr Warwick, said: "Margaret almost never spoke of Peter Townsend, but on the rare occasion she did, she told me that she knew nothing about what was going on behind the scenes and that nobody kept her abreast of developments.  "What is certain as a result of this letter is that she knew the Government was paving the way for the marriage if she wanted it and it proves that she was so much more involved in the process than she ever let on." Lady Mary Russell, a friend of Princess Margaret's, said that she had also always believed the Princess had little say in the matter and had been forced to give up Townsend because of the pressure to follow royal protocol.  She said: "We still felt it wouldn't be possible, not in that time, for her in her position to marry Peter Townsend, therefore when she did as she did, made the decision not to carry on, we were deeply sympathetic and sad for her."  The letter was discovered earlier this year at the National Archives in Kew in a file called "1955 Royal Family". It was found by a producer of Channel 4's The Queen, a new five-part docudrama based on pivotal events during the Queen's reign.  The first episode, Sisters, starring Emila Fox as the Queen and Katie McGrath as Princess Margaret, will be broadcast on November 29 and portrays the events leading up to the Princess' announcement that she would not marry Townsend.  A statement issued by Princess Margaret on October 31, 1955, said: "Mindful of the Church's teachings that Christian marriage is indissoluble, and conscious of my duty to the Commonwealth, I have resolved to put these considerations before others."  The Princess first met Townsend, a Battle of Britain fighter pilot, when she was still a teenager and he, twice her age, was married with two children and equerry to her father, King George VI.  After the king's death in 1952, he became Comptroller of the Queen Mother's household.  Their relationship was exposed after the Queen's coronation in June 1953 when a newspaper reporter noticed the Princess flick a piece of fluff from Townsend's jacket.  Shortly after the coronation, he was sent to Brussels for two years as an air attaché at the British Embassy in an attempt to quell the press interest in the scandal. Previously, a royal marriage to a divorcee had resulted in the abdication of Edward VIII to marry Mrs Wallis Simpson.  In May 1960, Princess Margaret married the photographer Anthony Armstrong-Jones. But the marriage was dogged by rumours of infidelity and heavy drinking, and the couple divorced in 1978.  The Princess died in February 2002 aged 71, seven years after Townsend died aged 80.
It was a famously doomed love story of a tragic princess who was forced to   give up the love of her life in the name of duty.