Our made-to-measure ruler

British history has traditionally been divided into sections named after the reigning monarchs. No other division of time - even the division by centuries - has the same immediate recognition. Some monarchs have become identified with the events during their reigns, or have become associated with movements in art, architecture or scholarship, others have merely defined a number of years limited by their accession and departure. To write a history of the past 70 years in the form of a royal biography must therefore make as much sense as any other division of the century, and in his introduction Ben Pimlott implies that this has been his intention. Nevertheless, the work is described as a biography, and clearly the roles of historian and biographer must in many ways collide.

Historians have often used the metaphor of society as a social pyramid. But the monarchy, in modern times at least, is not mediated through a series of structures downwards to the mass of the common people - it is associated directly with them, and indeed can only continue with their support. One of the most interesting questions about British society in the reign of Elizabeth II must be the nature and the extent of popular support for the monarchy and the extent to which it depends on the individual wearing the crown.

It may well be that there are no reliable means of testing a question like this in an instant biography. One of the cases against biographies of living subjects is that so much of the material needed to make serious judgements is by definition not available. Pimlott does look at two kinds of evidence to judge the degree and nature of popular monarchism. One, of course, is the attitude of the media. He also looks at some more principled and long-term arguments, particularly the work of Tom Nairn, which is in the main a hymn of hate against all things English, of which the monarchy is a reflection. Popular attitudes are incredibly difficult to judge or to predict, and perhaps the least convincing part of the book is its final conclusion that the institution of monarchy is unpopular while the present monarch retains her subjects' respect and affection. If this is indeed the case, it would seem to be because the younger members of the royal family have abandoned standards of behaviour that have come to be regarded as "traditional" for royalty, while the Queen's family background and her long rule reinforce the same "traditional" values.

More than any other part of the machinery of state and government, the monarchy is affected by chance factors of the age, sex and character of the holder of the office. Pimlott notes that in the 20th century three of the monarchs had not been born as heirs in the direct line to the throne. He might have added that in the last two centuries the small number of royals who were born heirs apparent had very short reigns. George IV and Edward VII might well have changed public attitudes to the crown had they come to the throne earlier and spent more than a short time at the head of the nation. By the time Edward VIII succeeded, the moral and familial image of the royal family had been so firmly established that his maverick behaviour was unacceptable to the church and government and he was forced to abdicate. The present monarch continues the tradition established by her grandmother, Victoria, and to a lesser degree by George III, of the monarch as staid head of the family in the home, the nation and the empire.

As the official biographer of an individual woman and a queen at that, the book has many necessary restraints. The public persona of a dutiful female monarch is historically much more important than her particular experience. Like her grandmother, Elizabeth II has presented a public image of joint head of a Christian nuclear family, stern in moral judgement, firm but reasonable in questions of state but in the main keeping a low profile on matters of policy, playing her part mainly in the decorative and ceremonial side of the nation's affairs. The very lack of drama or colour in her own life has made her a fitting symbol of a nation winding down its world influence. There are few apparent universally defining characteristics attached to the reign, though her name will certainly be given to the second half of the 20th century.

For political historians the most interesting part of the book is the account of the various points in which the Queen did become involved in the complex issues of postwar politics. Royal tours of the colonies and dominions and the accentuation of the familial image throughout the empire had become established by the early years of the century. The interwar years had in some ways reinforced the unifying role of the crown as the summit of a powerful empire. The years after the end of the second world war saw the emergence of powerful independence movements in the old colonial empire and increasingly the emergence of republican sentiments in the dominions. In some of these movements the Queen had two roles - as head of the British state and as nominal ruler of would-be independent states. In the negotiations over the declaration of a unilateral declaration of independence by the Smith government in Rhodesia, the Evening Standard cartoonist represented Ian Smith and Harold Wilson as chess players, moving the Queen across the board. It is in the close examination of this episode that some of the contradictions between the Queen as a person and the crown, "really a codeword for the government'', are demonstrated - a contradiction that can be contained only where the monarch is prepared to follow the guidance of her ministers. It is, in fact, one of the main arguments in favour of a monarchy that the incumbent is regulated by law and precedent and that the length of a reign makes it possible for the nominal head of state to understand the procedures and limits that must govern behaviour in a nonpolitical office.

The photographs in the book are extremely familiar to my generation. It is a useful reminder of some of the changes that have taken place in the media to look at the photographs of the two little girls in their fair-isle jersies and those coats with velvet half-collars and then at the most unkind Spitting Image cartoon of the Queen. We remember newspapers from France and America that arrived with bits cut out during the "Mrs Simpson" crisis, and the rhymes we chanted in the playground but never mentioned to our parents. The l se majeste of our cheekiest rhymes was nothing compared with the everyday tone used by modern comedians. To a large degree the mystery and seclusion of the royal family has gone, and it will be interesting to see how the public will respond to the Queen's golden jubilee early in the next century. We are no longer a nation in which street parties make any sense and the poor are not likely to be grateful for bun fights or pieces of commemorative china. Popular mass enthusiasm has perhaps been replaced by an attachment to a familiar devil and to a lack of enthusiasm for presidential systems as models for an alternative. It is an understandable contradiction that the main effect of reading this readable if necessarily uninspiring account is to set the mind running upon republicanism.

Dorothy Thompson is the author of Queen Victoria: Gender and Power.