Queen Elizabeth suffered a series of setbacks during the 90s, and she feared a new problem would appear "round every corner".
The 95-year-old monarch suffered a series of setbacks in the 90s, including Prince Charles' divorce from Princess Diana and a fire at Windsor Castle - and it took her a long time to overcome a sense of dread.
In “Queen Of Our Times: The Life Of Elizabeth II” - extracts of which have been published in the Mail on Sunday newspaper - Charles Anson, who was a royal press secretary at the time, explained: "It took a long time to get rid of that sense that, round every corner, lay a new problem."
Princess Diana died in a car accident in August 1997, at the age of 36.
And the Queen played a crucial role in the royal family's response to the tragedy.
Lord Airlie, the Earl of Airlie, told Lieutenant-Colonel Malcolm Ross and his colleagues at the time: "I said, 'The one thing is this – don't look at a file. This has to be de novo.' In other words, this had to be done quite differently."
Lord Airlie subsequently wrote a memo to the Queen outlining a general plan for Diana's funeral.
He says now: "For instance, the importance of catching and reflecting the public mood of 'the people's Princess', and ensuring that the ceremony was not overwhelmed by officialdom. I felt, too, that the procession of the coffin to Westminster Abbey should break with tradition and be somewhat radical."
The Queen then gave the go-ahead to a royal funeral that broke with tradition.
Recalling the Queen's reaction to the "radical" suggestions, Lord Airlie said: "The answer came back, saying, 'Go ahead.' So that let Malcolm Ross and his chaps get on with the job, which they did brilliantly."