Commoner chameleon

Whom to marry never used to be much of a problem for British princes. The choice was limited to members of the Protestant royal houses of Europe. After the First World War, however, the need for the monarchy to become distinctly British made links with foreign dynasties less desirable, and members of the royal family were permitted, even encouraged, to marry subjects. But which sort?

The public loved royal marriages, but demanded that they be romantic; at the same time, the monarchy's dignity had to be maintained. If the aim were popularity with the people, there was little evidence the public would welcome the marriage of a prince or princess, still less an heir to the throne, to a commoner who was too common. Indeed, until the marriage of Queen Victoria's daughter, Princess Louise, to the Marquis of Lorne in 1871, no royal had married a subject since Henry VIII.

If royal were not to marry royal, members of the British aristocracy were the obvious choice. The success of the marriage of Elizabeth Bowes-Lyon to the Duke of York, later King George VI, suggested that matches with the less fashionable or racy members of the aristocracy were safe, while Edward VIII's abdication demonstrated the dangers of leaving the choice of bride solely to a prince's romantic urges.

In practice, during most of the 20th century, the royal family veered between the traditional practice of marriage with foreign royalty - as with Princess Elizabeth's marriage to Prince Philip of Greece - and union with members of the aristocracy, although the sorry saga of Prince Charles' marriage to Lady Diana Spencer cast the latter course in doubt. Hovering over all decisions was the tension between the need for romance and the security of the monarchy.

It might have been expected that, with changing social mores and the ditching of the guidelines preferring a royal or aristocratic (not to mention virginal) bride, Prince William had only to worry about balancing his own inclinations with the needs of dynasty and nation. Judging by the approbation greeting his engagement, he has done so, but the media interest in Kate Middleton's social background suggests that the question of "if a commoner, what sort of commoner?" still applies. Her place in the social order has come under the sort of scrutiny that the Habsburgs would have reserved for a princess' lineage. She is, we are told, a "Boden bride" and her engagement to William marks a triumph of, variously, the middle class, the upper-middle class or the middle-middle class.

The social order may have changed, but it is more complex and paradoxical than ever before. Princess Marina, Duchess of Kent, is said to have referred to the future Queen Mother and the Duchess of Gloucester as "those common Scottish girls". All things are relative, but today few people - even dukes - claim to be upper class. David Cameron, who resigned from White's club in 2008, insists he is middle class.

Nature abhors a vacuum, and the disappearance of the upper class has been followed by an intense interest in the distinctions that demarcate the rungs of the middle orders. The press quotes unnamed "friends" of Prince William making derisory comments about Kate for being the daughter of an air hostess, and snickering "doors to manual" behind her back. If true, they are now probably reflecting ruefully on the Victorian dowager's adage: "Always be nice to young girls. You never know who they are going to marry."

The paradox is that the job of air hostess is widely seen as glamorous and desirable and that to most people the Middleton parents, living in rural England and owning a successful business, seem rather posh. But they are, we are told, socially ambitious - a dreadful solecism, when decent folk are content with their station.

We don't and never will live in a classless society, which would probably be rather boring; while royalty have, in any case, traditionally been more of a caste than a class. If reactions to this royal engagement point to how much we all enjoy positioning people and to snobbery both straightforward and inverted, it also demonstrates both the mobility of modern British society - Kate's great-grandfather was a miner and she went to Marlborough - and the social and cultural changes since Prince Charles' engagement in 1981.