At first, some journalists mistakenly thought it was a picture of a naked Cherie and got more excited than during an election campaign, but it soon emerged that this was part of an unplanned publicity stunt by the fashion designer Paul Smith.
A bright spark at the Mail on Sunday who had no interest in the politics noticed Blair was wearing much more trendy designer gear than usual. A call to Paul Smith's PR department confirmed it was their clothes. According to the MoS reporter, the press office spotted the PR opportunity and 'sang like a canary' about how the Prime Minister was decked out in their gear - and even gave the MoS the story about the nude on the cuff.
The paper couldn't believe its luck in finding out about Blair's little secret. The fact that British punters are far more interested in what Blair wears than what he says gave the story impact.
As soon as the MoS hit the streets, the Paul Smith PR department was inundated with calls from hacks all over the world wanting to know more.
But Downing Street had got there first. 'Tony wears a tart on his sleeve' was not the sort of headline they were looking for.
As Paul Smith himself is close to Blair and has been ennobled by New Labour, it didn't take long for Downing Street to get the message through to the company that the Prime Minister would prefer it if they said nothing.
We then had the farcical position where Paul Smith's people refused even to confirm that Blair wore its gear, even though they had originally co-operated with a PR stunt as transparent as a see-through blouse.
As the conference dragged on, it emerged that Blair had been decked out in different suits, ties, shirts and trousers from the Paul Smith range and was looking more like a fashion model than a prime minister. My spies in Downing Street tell me that Tony was forced to wear all this trendy gear by Cherie, who was horrified that he was voted one of the worst-dressed men in Britain by GQ magazine, which has Peter Mandelson as a columnist.
Even Gordon Brown, who often looks like he has been dragged through a hedge backwards, was voted a better dresser. For years, Sarah Brown has been choosing Paul Smith ties for her husband and Cherie thought he could do the trick for Tony.
On balance, I suppose that Blair has not come out of the episode too badly. I reckon most people expect their leaders to look half-decently dressed when representing their country abroad. But what about Paul Smith? Will the punters now be besieging the shops to buy gear that Blair wears? I think not. I've already sent my Paul Smith tie to Oxfam.
It was probably the realisation that Blair may not be the best model for their trendy gear that shut them up rather than orders from Number 10. A 48-year-old father of four is not exactly what the PR department had in mind when promoting Paul Smith clothes.
It would be wise for companies to beware of using politicians to sell their goods. The only decent PR stunt involving a politician that I can recall was when Irn Bru sent Gordon Brown a crate of their drink before his first Budget when they found out he wouldn't be drinking the traditional glass of scotch whisky during the speech.