Gormlessly pausing to enjoy the Changing of the Guard at Buckingham Palace one day, I was accosted by a foreign tourist who was very certain of his rights. "So, when does the Queen come out?" he said. "Well, I don't think she's going to," I said. "It's the middle of the week, it's raining, and she's probably got better things to do. Anyway, she's in India, now I come to think of it." "She's not going to come out?" he said, incredulously. Having seen a hundred clips of Her Majesty emerging serenely on to the balcony, he was under the impression that she popped in and out all the time, like a cuckoo in a clock. That, he clearly believed, had been promised as part of the package.
How much better they arrange things elsewhere. It won't be long before any British tourist visiting South Africa is granted a cup of tea with Mr Nelson Mandela. The Spice Girls, I believe, set the whole thing off with what at the time seemed a truly surreal photo-opportunity, but since then it has sometimes seemed that anyone with any claim to fame finds it possible to get half an hour with the great man. Starlets you last saw gurning in an obscene Julien Macdonald confection outside the British Soap Awards are suddenly demurely photographed holding Mr Mandela's mildly bemused hand. Alan Titchmarsh, Charlie Dimmock, Morgan Freeman, Naomi Campbell, Michael Jackson, and for all I know Mr Lawrence Llewellyn-Bowen have all made the pilgrimage, and, incredibly, have not been told to push off.
The latest pilgrims are the England football team now visiting South Africa, who, after playing a friendly with the national squad, are down to pay the ritual visit. Is Mr Mandela a football fan? Well, it hardly matters, any more than anyone really wants to know whether he had ever heard of the Spice Girls before they inflicted themselves on him. The point of this is to bring two massive contemporary icons together, and the photograph everyone wants is Mandela and David Beckham shaking hands. The image is the whole point: whether it signifies anything much apart from an affirmation of Beckham's A-list status is a question few will have the bad taste to ask.
The Mandela pilgrimage closely resembles a visit, not to a retired politician, but to a spiritual leader. Anyone can turn up and book an audience in the near future with the Dalai Lama or the Pope. Mandela is much more exclusive than that, but he is a nice enough man to admit all sorts of celebrities to his presence, and grant them an audience, half spiritual, half raucous publicity.
Mandela is useful for this purpose because the specific reasons for admiring him long ago faded away, and by now he is a sort of blank space on to which anyone can project any vague idealism. It is a fair bet that if an interviewer asks a celebrity which living person they most admire, the answer will, more often than not, be "Nelson Mandela". Of course, he is admirable, and the answer may sometimes be deeply considered, but in most cases I suspect that it is an automatic response. He is a safe choice, because he patiently endured long incarceration and presided over the liberation of South Africa. Anything more detailed than that - the knowledge of his views on the war in Iraq, on globalisation, on ecological issues - would not be very helpful. The idea that Mandela might actually be a man with whom you could disagree on some issues is by now frankly bizarre.
"He's the one man in the world," someone observed to me, "who you wouldn't want Ali G to take on." It's absolutely true, and the reasons why are suggestive. It is not, I think, that Mandela has such moral authority that a satirical attack would seem grotesquely offensive. It is more that Mandela's virtues have been established as so unspecific that a suspicion has baselessly arisen that a satirist could quite easily make him look ridiculous.
Figures of comparable authority seem, in some way, less vulnerable. If Ali G, in the course of his American adventures, had somehow inveigled his way into interviewing Bill Clinton, nobody can doubt that the ex-President would have emerged unscathed. When a Canadian radio journalist astonishingly managed to hold a telephone conversation with the Queen, posing as the Canadian premiere, he was quite unable to score a single point.
Somehow, we wouldn't want to run the risk of anyone irreverently challenging Mandela in this way, because at some level we don't quite know what would happen. In reality, I'm sure, he is tough as old boots, and just as capable of taking care of himself. The fact that one does entertain these suspicions is nothing to do with him; it is a consequence of the function we now permit him to fulfil, which is an international presence of vague saintly benevolence. Behind that, anything at all might be found. Photo-opportunities with TV makeover queens and overpaid footballers do a general disservice to the wily, ruthless politician. At some level, we don't consider Mandela someone worth arguing with. That will make any expressions of admiration sound distinctly hollow.