When was the last time a visiting dignitary caused such excitement? When did we last see our leaders, coiffed and groomed, rehearsing their most beatific grins in preparation for a fleeting photo opportunity with a foreigner? When did our wisest columnists and leader writers last display that collective giddiness in their prose?
You are thinking, maybe, of Pope John Paul II's historic visit in 1982, or John F Kennedy calling on the Queen in 1961, but no, you need only go back to March, and the state visit of Carla Bruni.
Then, critical faculties were cast aside and judgement was numbed by the glamour of it all. She was "triumphant", she won "rave reviews", she passed her "first big diplomatic test", she left us with "the world at her feet" - and that was just in the Daily Telegraph. Quite an act for Barack Obama to follow.
Readers of this magazine, benefiting as they do from the insights of Andrew Stephen, are in no doubt about the complexity of Obama's politics and the obstacles cluttering his path to the White House, but they (you) are also aware that he is more than just another politician in a suit. He has something special.
To Gerard Baker in the Times, he is the Fab One, whose Atlantic crossing has provoked a "pregnant excitement" reminiscent of Beatlemania. To John Rentoul of the Independent on Sunday he is "Bill Clinton and Nelson Mandela rolled into one". Timothy Garton Ash has written in the Guardian that Obamamania probably surpasses even Dianamania as a global phenomenon.
Much has been written about the ingredients of this specialness. There is the simple, delicious fact that he is not George W Bush - but then neither is John McCain, the Republican presidential nominee. More potent is what Stryker McGuire, the London-based contributing editor of Newsweek, calls "the great narrative". "Here is someone with an African father and a mother from the Midwest, who grew up outside the US and went to Harvard Law School before becoming a senator: it is an American success story."
Inspiring it is, and that bit fresher and more modern than McCain's backstory of Vietnam heroism, but it takes us only so far. That he is lean and handsome still doesn't make him a crowd-puller. Nor do mockable lines such as "We are the ones we have been waiting for". Not even that he is black, or half-black, if you prefer, explains his magnetism - remarkable as it is for a black man to get this close to becoming president, it is just a fact rather than a feeling, and it is surely a feeling that sets him apart.
I haven't seen him, or heard him speak, but for months I have been accepting the word of journalists and writers in papers across the political spectrum who have been insisting he is special.
In the Telegraph Lionel Shriver wrote, after that speech about race back in March, that Obama was "a worthy man" and "more eloquent than any American politician of my adulthood". Mary Ellen Synon wrote in the Daily Mail that he had "said things that were far braver and more decent than anything anyone has heard from any Democrat in a generation". The Independent's Matthew Norman, not one of life's natural hero-worshippers, declares himself "a founder member of the British Obamaniacs Association".
With this specialness now on tour, we want to know what it's like close up. But as McGuire points out: "Charisma has to be felt in person." We couldn't all meet or see the man, so why the fuss?
Curiously, in this globalised century, a televised soundbite in Downing Street, against our domestic backdrop and among our grinning politicians, is still more potent for us than a televised speech among strangers in Philadelphia. That, after all, was why a couple of days of Carla Bruni in London last spring was more exciting to us - and seemed to suggest different things - than a year of Carla Bruni reported from across the Channel in France.
Let us pause one last time, before the opportunity slips away, to reflect on the collective shame of the Daily Mirror, Sunday Mirror, Daily Record, Daily Mail, Evening Standard, Metro, Daily Express, Sunday Express, Daily Star, Sun and News of the World, which confessed to libelling Robert Murat more than a hundred times between them, in what can only be called an orgy of sustained irresponsibility.
If abuses on such a scale happened in any other industry - pharmaceuticals, food, railways, banking - the front pages of those same papers would be on fire with demands for heads to roll, for a public inquiry, for transparent measures to ensure that no such outrage could happen again.
Instead we have a six-minute court hearing, pocket-money damages and a muttered "sorry". What a bunch of hypocrites the owners and editors of these newspapers are.
Brian Cathcart is professor of journalism at Kingston University