Lord Charteris, 81, who claims that he thought the remarks had been made off the record, predicts that the Prince and Princess of Wales will divorce.
"Divorce will clear the air. And, yes, of course he will be King. There is nothing in the constitution to say the monarch must be happily married. When the dear sweet Queen dies, although I wish she could go on forever, a council of succession will appoint Charles as head of state."
In an interview published in The Spectator magazine, Lord Charteris, who retired in 1977 after five years as private secretary to the Queen, and 28 years in all at the Palace, explains that he was hired informally through a social network, so was never asked to sign the Official Secrets Act.
He said that "of course" Camilla Parker-Bowles was the love of Prince Charles' life. In time people would forget that he had confessed his adultery with her, and remember his honesty. The Queen has the same view, he confides. She "is enough of a realist . . . to know there is nothing for it but to sit it out. She believes the monarchy is strong enough to withstand change and analysis."
Lord Charteris added the the Prince is "such a charming man when he isn't being whiny".
Lord Charteris is quoted as describing the Queen Mother as "a bit of an ostrich - she has learned how to protect herself. What she doesn't want to see, she doesn't look at."
He said the Royal Family does not feel any less secure, nor do they feel their roles are diminishing, or that they themselves are becoming anachronisms.
"Lampooning, ridiculing, has all been done before," he argues. "They know about these phases. The Queen is aware that they have gone through problems before and survived, and so they will do again.
"If the Prince and Princess of Wales had had a successful marriage, there would not be a problem."
Reluctantly he agrees with his interviewer that there is room for streamlining the Royal Family: "It's only the monarch who matters, although it is lovely when you see everyone together at a great state occasion."
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