Britain's Prince Philip described the week after Princess Diana's death as a "nightmare" for the royal family.

Prince Philip

Prince Philip

A letter half-written and half-typed from the prince to his niece, Princess Margarita of Baden, has revealed his thoughts on the devastating days following the late Princess of Wales' fatal car crash in Paris on August 31, 1997 - and the note has now been sold at auction for £2,300.

According to the Daily Mirror newspaper, the letter, which was dated September 5, 1997, was personally signed by Philip and features his reactions to the criticism the royals faced for their apparent lack of public mourning.

He also spoke about the reaction to him and wife Queen Elizabeth "forcing" Diana and Prince Charles' sons, Princes William and Harry, to church in Balmoral, Scotland, shortly after the incident.

He wrote: "We have even been criticised for 'forcing' the boys to go to church on Sunday, the day of the accident."

Philip insisted in the note that churches are used for praying in and that the death of the princess - who was just 36 years old - was difficult enough to deal with.

Philip and Queen Elizabeth faced criticism from members of the public at the time for not speaking publicly about Diana's death or flying the Union Jack at half-mast over Buckingham Palace.

However, the family did release a rare statement four days after her passing.

It read: "The princess was a much loved national figure, but she was also a mother whose sons miss her deeply.

"Prince William and Prince Harry themselves want to be with their father and their grandparents at this time in the quiet haven of Balmoral."