What is it that people play out when they get themselves photographed in front of the Taj Mahal? Sometimes these people are famous, powerful or beautiful, or all three at once. Sometimes they are a couple, sometimes alone. Most often they are perfectly ordinary people. And when they are not, then romance and proximity to the sublime give them a halo that is, for a few moments, different from their usual way of being celebrity. As a backdrop, the Taj humbles all to their ordinary humanity, but also invests people with a different kind of remarkableness and pathos.

Most Indians have better things to do and watch on their Republic-Day holiday than the parade in Delhi or its chief guest. Nor would they have been terribly interested in the French president’s visit, had Carla Bruni not spiced things up like this. But the prudish flutter in Delhi over what to do with Ms Bruni, and her mildly exasperated decision to ‘spare’ India the embarrassment of a president visiting with his lover, invest Nicolas Sarkozy’s visit to the Taj with a somewhat ridiculous air of uncertainty. Will he be alone there, or will he be a couple? And how ‘private’ would such a visit be? After being president and chief guest at the parade, followed by the ‘At Home’ at chez Patil, would the Taj do its levelling trick and turn Mr Sarkozy again into just somebody’s boyfriend?

Diana, Princess of Wales, had posed alone in red and pink on that marble seat, in all her enchanting forlornness. This was 1992, and she was visiting with the prince. But a few months later, Andrew Morton’s book would tell the world her “true story” of self-harming unhappiness. Photographers still recount how she ordered them to photograph her in exactly that pose in front of the Taj. Her parents-in-law had also visited the monument in 1961, but in moonlight. So there are no photographs. Instead, the Queen and her husband posed for pictures behind the corpse of a 9½ feet tiger, which the Duke of Edinburgh had shot himself. The Queen stood at the centre, holding a home-movie camera and flanked by two elephants complete with howdahs. That proved to be a more robust marriage, by Windsor standards. The next year, Jacqueline Kennedy stood in front of the Taj, radiantly chic in her first-ladyhood. She wore a blue-and-sea-green dress and white gloves, and she came back at night for the moonlit view. Life reported how, for a while after that, the locals would refer to her as “Ameriki Rani”. If marble had a memory, then this seat would tell of other presences: the Clintons (separately, once just mother and daughter), the Musharrafs, the Rongjis from China, and so on.

Couples come and go, marriages are made and unmade, and protocols kept, broken or improvised. But the wonder of marble and moonlight — cold but magical stuff — lets it all happen, with girlfriends, wives and First Ladies alike.