But in this time of intensified interest in the machinations of the British royal family, Valentine Low delivers a timely, incisive account of the advisers, who, "exert power, but do not rule" in these closed-off households.

Low's revealing account was written just before the death of Queen Elizabeth II, so she is cited in the present tense and King Charles is still a prince. Low interviewed nearly 100 key individuals, who have worked in the royal households from the 1960s to the present day, with a focus primarily on the powerful private secretaries and press offices.

Apart from several key Australian figures, most advisers have come from a background of top British public schools, Oxbridge and the aristocracy. Low writes, "There is a reason why those closest to the Queen are drawn from such a narrow social circle: it is because the Queen is a woman of a certain generation and class, and they are the people she feels comfortable with".

Michael Adeane, educated at Eton and Cambridge, the Queen's "tweedy, cautious" private secretary between 1952 and 1972, observes, "It is no use thinking you are a mandarin. You must also be a nanny."

Nonetheless, as Low comprehensively demonstrates, those around the Queen have exercised, and presumably still exercise, considerable power behind the throne. The snuff-loving old Etonian Martin Charteris, private secretary from 1973 to 1977, certainly exhibited power in the palace letters to Sir John Kerr before and after the 1975 Gough Whitlam dismissal.

Alan "Tommy" Lascelles, "epitome of the old school Palace insider", was a key influence in the ending of Princess Margaret's relationship with Group Captain Peter Townsend in the 1950s. Princes Margaret and Townsend were not the only ones to run foul of royal advisors; Princess Diana called them "the men in grey suits", Sarah Ferguson termed them "constipated, self-appointed keepers of the gate", while Prince Harry and Meghan Markle's antipathy to them is decidedly ongoing.

Low's first chapter begins with a story of a senior Australian member of the royal household, almost certainly William Heseltine, being informed at Australian immigration as he handed in his passport, "Mate, there's no T in courier".

Australian-born, Heseltine was the Queen's private secretary from 1986 to 1990, but had been involved in the royal household since 1960, when he was seconded from Robert Menzies office to be assistant press secretary at Buckingham Palace. Heseltine is credited with influencing the 1969 TV documentary on the royal family, as well as encouraging their walkabouts.

Another Australian, Samantha Cohen, a former assistant private secretary, was about to retire in 2018 after 17 years at the palace. She was, however, persuaded in 2018 to "stay on and help" Prince Harry and Meghan Markle, becoming their interim private secretary. Low traces their declining relationship, including the troubled Australia Fiji tour in 2018, with Cohen eventually falling out of favour and becoming one of the increasing number of the "Sussex Survivors Club".

Indeed, Prince Harry's 2023 reflections on leaks from Camilla's press office go back to the Charles and Diana divorce.

Low analyses Mark Bolland's PR, which helped transform Camilla "from the most hated woman in Britain to the country's future Queen". Low quotes a Palace insider that Bolland, known as Lord Blackadder by William and Harry, was "a master of the dark arts, a courtier you could recognise from other eras manipulative, clever and devious".

What of the future? Low notes that Christopher Geidt, the Queen's private secretary from 2007 to 2017, was a supporter of "modernisation" in household operations, although his downfall came partly through trying to reform the archaic and different management structures.

Charles comes across as a hard taskmaster, primarily "because he is very demanding of himself". This is reflected in his office turnover. Charles, for example, had five private secretaries in seven years from 1985 to 1992, while his controversial ex-valet Michael Fawcett, who ultimately wielded significant political and financial power, culminating in becoming CEO in 2018 of the Princes Foundation, had to resign in 2020 because of alleged financial "skulduggery".

Low describes the King's last private secretary as Prince of Wales, Sir Clive Alderton, as "a schemer, a chess player . . . a figure from Wolf Hall or House of Cards".

Now, at a pivotal moment in its history, the question of who advises the royal family and helps "decipher the (royal) code", especially in the light of Prince Harry and Meghan Markle's public revelations, will be more important than ever.