Lady Glenconner said the late Princess had not wanted to end up at Frogmore in Windsor Great Park, where Queen Victoria and Prince Albert are buried. Instead, she preferred the Royal Crypt at St George’s Chapel in the grounds of Windsor Castle, where her father King George VI is buried.
"She told me that she found Frogmore very gloomy," said Lady Glenconner, a former lady-in-waiting to the princess.
"I think she’d like to be with the late King, which she will now be. There’s room I think for her to be with him now. She just said she was going to be cremated. I think she wanted her family and her friends at her funeral. Obviously, later on there will be a memorial service when her charities will be represented, but for her actual funeral she wanted it to be as private as possible."
Friday’s cremation will be will be a 280 service at the municipal crematorium in Slough, a major break with royal tradition. No members of the Royal Family will be present in the 1960s, stained brick crematorium and the princess’s ashes will later be carried without ceremony to St George’s Chapel in Windsor, where they are to be placed in the Royal vault. The last member of the Royal Family to be cremated is believed to have been Princess Louise, Duchess of Argyll, daughter of Queen Victoria, in 1939.
Yesterday, the Queen, dressed in black, briefly returned to her official duties by opening a homeless hostel in London - as Buckingham Palace confirmed she would not be attending Slough crematorium on Friday.
Princess Margaret’s cremation will be one of six at Slough crematorium on the day. Roger Parkin, the registrar, said: "As far as we are concerned, it will be a normal working day."
He added: "Friday is actually quite quiet. We’ve only got five others on the books at the moment. ."
For those who do not live within the administrative boundaries of Slough Borough Council, the charge levied for a cremation is 280, which includes the provision of a CD or cassette player to play any choice of music.
Mr Parkin said: "It all depends on what exactly the family wants. Our tradition is we tend to have people in at least a week after they have died to give the families a chance to get everyone together. But this is obviously a slightly different situation. I hope the other five families on Friday don’t get disrupted by this or I would feel very sorry for them."
The crematorium, which performs 1,800 cremations a year, was built in 1963 and, apart from Princess Margaret, the only other famous person to have been cremated there was the comedian Ernie Wise, three years ago.
The crematorium seats 80 people but for Princess Margaret, the witnesses will be restricted to representatives from her household and from the Lord Chamberlain’s department. Families - usually 15 a day - are given a 25-minute "slot" for their service.
The funeral service is to be led by the Rt Rev David Conner, the Dean of Windsor, who will then travel with the coffin the eight miles to Slough .
Her ashes will be returned to Windsor where they are to be placed in the Royal vault at St George’s Chapel, alongside her father’s tomb.