The influence has been behind the scenes and always subtle. But its general drift is clear and not confined to attempts to temper the excesses of the later years of Thatcherism. The sovereign is, as Professor Pimlott yesterday put it ,"in her own way, a bit of a lefty".
The book, which is being serialised in The Independent over three days, starting today, is based on 85 interviews with members of the royal family, senior courtiers and the Queen's closest friends. Many of the interviews were facilitated by Buckingham Palace, which also allowed unprecedented access to the royal archives.
Pimlott, professor of politics and contemporary history of Birkbeck College, London University, reveals that the monarch questioned the wisdom of the British invasion of Suez in 1956. She expressed anger at the Government's acquiescence in the US invasion of Grenada in 1983. She made it clear she was out of sympathy with Margaret Thatcher's opposition to sanctions against South Africa. And she let it be known that she was concerned over the general drift of Thatcherism, which she saw as damaging Britain with its uncaring attitude towards the under-privileged.
The Queen also made the Thatcher government aware that she thought it was undermining the Commonwealth and threatening the consensus in British politics which she thinks has served the country well since the Second World War.
The role of the monarch as part of the system of checks and balances which have developed in the British constitution has, in previous times, always been perceived as a check on left-wing politicians. "George VI's `gnashes' had sometimes focused on the Labour government's attacks on private property, and the Queen Mother continued happily to talk to all comers about the misdeeds of communists and left-wingers in the Labour Party or at the BBC," Pimlott writes.
But the present Queen has acted more consistently as a check on the right. Her position over Suez was far from neutral in the face of Sir Anthony Eden's insistence on a dying thrash of Empire by invading Egypt. "I think the Queen believed Eden was mad," the book quotes one senior courtier as saying.
In more recent times the Queen made it clear that she thought the Thatcher government should be more caring towards the poor and that she had feared that serious long-term damage was being done to the social fabric of the nation during the 1984 miners' strike. She also had doubts about the decision to allow the Americans to use British airbases for a raid on Libya in April 1986.
The Queen's displeasure was expressed with circumspection but, in the circumstances, it was no less forceful for that. "She did not directly criticise the Government's plans. But she measured her response to them," Pimlott writes. "She would often express, or hint at, her own opinion by asking a leading question, or referring to somebody else who held an alternative view. If she approved she would say so, positively. Disapproval was indicated by a significant failure to comment."
Such is the Queen's style in general, the book reveals. Unlike her husband, the Queen seldom indicates directly what she wants to happen. "She has excellent passive judgement," one former courtier says. She expects others to make suggestions, and then she reacts with caution, reserving her most positive responses for ideas which fit her own needs precisely.
Pimlott reserves his greatest criticism of the Queen for her role in the backroom handover of power between the Tory prime ministers Harold Macmillan and Alec Douglas-Home. She allowed Macmillan to dupe her in what Pimlott describes as "the biggest political misjudgement of her reign". As a result of "the Macmillan-Home debacle" the Conservatives changed their method of selecting their leader. This put an end to the monarch's discretionary power in the choice of a prime minister in normal circumstances.
But, he argues, the manoeuvrings around the formation of the minority Labour government in 1974 show that the monarch still retains a significant role. Though the Queen's prerogative powers were never invoked, a belief in the possibility that they might be played an important part in the inter-party political poker game. In the multi-party conditions thrown up by a volatile electorate - and in the event of a hung parliament at the next general election - it might be a crucial one.
Queen and Country, pages 18 and 19