Diana's letters to Queen Mum destroyed for being 'too private'

With the thoughts of the late Queen Mother published in an eagerly-anticipated new autobiography this week, secrets from inside the royal family have been uncovered.

Letters from the late Princess Diana to the Queen Mother were destroyed by Princess Margaret "because they were too private", the book reveals.

The biog does, however, shed light on the matriarch's views about what she saw as Diana and Prince Charles "washing their dirty linen in public" during their separation.

"It's always a mistake to talk about your marriage," she said in a taped interview after Charles admitted his infidelity on television.

The book, by William Shawcross, includes numerous transcripts which the Queen Mother secretly recorded before her passing in 2002 at the age of 101.

The publication also describes how she narrowly escaped death by a German bomb during the Blitz, and how she opposed the imposition of tax on the royal family.

Queen Elizabeth, The Queen Mother: The Official Biography is on sale from Thursday.