Joan Smith: A royal wedding suits this celebrity age

With all eyes on a burgeoning princess, the Royal Family can cling unnoticed to its outmoded practices

One day last week, a woman went out in a coat she'd worn before. With a swooning sense of déjà vu, picture researchers accessed archives and established the exact date and occasion, along with the revelation that several inches had since been removed from the hemline. The thrifty woman in question went on to pour a bottle of champagne over an inflatable dinghy, a task she carried out with such ease that she was judged to have passed "a crucially important milestone".

It's the Diana effect: tellingly, this trifling event was recorded in a mass-circulation newspaper next to a link directing readers to "more celebs". Thanks to the late Princess of Wales, Kate Middleton has been elevated to the front rank of international celebrities. Her picture now routinely appears alongside paparazzi favourites such as Victoria Beckham and Katie Price. Unlike the latter, Middleton can be trusted not to blurt out cringe-making revelations about her sex life, but class is no guide to future reticence. Prince William's fiancée is undeniably posher than Price but nothing like as posh as the late princess, who had few inhibitions about spilling the beans when it suited her.

Thirty years on from the marriage of Charles and Diana, that of their elder son is a good moment to take stock of the British monarchy. In 1981, it was a distant institution, with so little known about its intimate relationships that people still talked about the decision of the Queen's mercurial younger sister, Princess Margaret, not to marry a divorced man. For most, the monarchy was simply there, while its rituals – the state opening of Parliament, the Queen's Christmas broadcast, occasional weddings and funerals – were both comforting and predictable.

Lady Diana Spencer changed all that. Marrying into the Royal Family at a moment when media outlets were about to proliferate, the princess's revenge for an unhappy marriage was modern in at least one sense. Marrying for what she imagined was love and finding herself in a miserable dynastic marriage, Diana used the media to get public opinion on her side, subjecting the Royal Family to a degree of scrutiny it had never expected. If Diana could not be queen, she would be a celebrity worldwide. The extravagant scenes of mourning that followed her unexpected death reflected the success of this strategy.

It was visibly uncomfortable for members of the Royal Family to find themselves in this situation, but there is also a sense in which Diana did them an enormous favour: the elision between royalty and celebrity is now so complete it shields the institution from less comfortable forms of scrutiny. Fevered speculation in the media about Royal Wedding trivia, such as who will make the bride's dress, plays to an undiscriminating appetite for news about famous people. It also creates an impression of gathering excitement in the country. Like so many matters relating to the monarchy, this is hard to judge by objective criteria.

Take VisitBritain's claims that the Royal Family brings £500m into the British economy each year and that the wedding will boost tourism. Both claims have been challenged by Republic, the organisation that campaigns for an elected head of state, which says that internal documents obtained under the Freedom of Information Act show a different story. There has certainly been an unexpected coda to a flurry of articles about foreign tourists flocking to Britain for the Windsor-Middleton wedding: Gareth Williams of the flight-comparison site Skyscanner has noted a surge in searches by people who want to leave the country on or around the date of the royal wedding. "We have... seen a 275 per cent increase in searches from Brits looking to make the most of the extra holiday and escape the UK and the wedding hype," he observed.

Polly Toynbee tried to make this point on Radio 4's The Long View last week, only to be contradicted by the veteran royal correspondent James Whitaker. He insisted that all those globe-trotting Britons would be begging for facilities to watch the wedding on TV in their hotels, and refused to countenance Toynbee's argument that some of us aren't remotely interested in the event. At the same time, his repeated references to Middleton as a "commoner" and her lack of "royal blood" spoke volumes about the snobbery still associated with the Royal Family.

The case against the monarchy – that the institution is expensive, unfit for purpose and has a chilling effect on social mobility – rarely gets a fair hearing. That's due in part to the lack of reliable information about the monarchy; the Royal Family enjoys enviable exemptions under the Freedom of Information Act. The much-quoted claim that it costs taxpayers only 67p per person per year does not include one of the most significant costs: providing security for the Queen and her extended family. According to Republic, the Royal Family costs 100 times as much as the Irish presidency, and it's certainly hard to imagine an elected president costing as much as the Windsors.

The most damning charge against the monarchy post-Diana is that it has failed to modernise. The Queen is head of state of a democracy in which deference has declined, merit is supposed to be more important than birth, and a growing minority supports the proposal that we should become a republic like Germany or France (both of which, by the way, manage to attract tourists without having a royal family). But the Queen remains a distant and unaccountable figure, surrounded by courtiers who ensure that she meets only a few carefully selected members of the public. At Buckingham Palace garden parties, most of the guests get no more than a fleeting glimpse of the monarch and her relatives as they process from the back of the palace to the royal tent.

Two or three years ago, I was introduced to the Queen at a Christmas party in the palace. Obviously, I didn't curtsy but I smiled warmly and said hello; the Queen stared, said nothing and, after a moment, moved on. It was a fascinating encounter: not just republican meets monarch but informal good manners versus inflexible protocol. It sparked a fantasy in my mind in which Peter Tatchell had been elected president, striding into the room in red trousers and shaking everyone enthusiastically by the hand.

This year's Royal Wedding will have considerably less impact on the Windsors than the Prince of Wales's first marriage, in 1981. Diana Spencer brought youth and glamour to the Royal Family, and Kate Middleton will give royal correspondents something new to write about. But the reflexive sexism that's already emerged – commentators are vying with each other to insist that her role is to stay in the background, support her husband and produce children – is breathtaking. Marrying a privately educated woman from an affluent background is hardly a radical departure from tradition. Becoming a monarchy that appears in Hello! is as modern as the British royal family gets.

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