Lobby journalists finally lost their patience with Tom Kelly at the Iguazu falls on the border of Brazil and Argentina.
After days of trailing through South America after Tony Blair's party, with barely any access to the great man, the travelling press pack turned on his mouthpiece.
Temperatures rose as irritated reporters berated Mr Kelly, who had only been the Prime Minister's official spokesman for a matter of weeks. Despite his short time in the post, he had already gained a reputation for stonewalling requests from the media for useful information.
Realising that the journalists' patience had been stretched to the limit, he said: "I'll see what I can do."
Minutes later, he returned with Mr Blair and his wife Cherie, who then spent half an hour mingling with the press party.
Mr Kelly had learned early on that excessive reticence, born out of loyalty to his boss, could rebound on him.
The irony of this week's episode is that the tasteless use of the colourful term "Walter Mitty", also inspired by loyalty to No 10, has threatened his future in the job.
Mr Kelly had first come to the attention of the Prime Minister and his previous official spokesman, Alastair Campbell, during the tortuous negotiations between the political parties in Northern Ireland.
A former producer of the BBC2 programme Newsnight and head of news at BBC Northern Ireland, he switched careers to become director of communications at the Northern Ireland Office in Belfast shortly after Labour came to power in 1997.
He impressed the Secretary of State for Northern Ireland, Mo Mowlam, and her successor, Peter Mandelson, with his sureness of touch and ability to articulate the Government's message. He also managed to build the trust and respect of journalists across the political spectrum.
Mr Kelly, who has four children and is in his 40s, also proved a wily operator in the realm of office politics,successfully guarding his domain when a London journalist-turned-spin doctor was brought to Belfast by Ms Mowlam.
There was, however, a moment of farce when he was forced to deny claims that a police dog had growled at Mr Mandelson. In a statement, he said the black labrador had been "disciplined and entirely under control" when Mr Mandelson crouched to stroke it.
When Mr Campbell - who had seen him operating at first hand as the Prime Minister spent more time in Northern Ireland - decided to retreat to the shadows, Mr Kelly was an obvious choice to share the job with Mr Campbell's deputy, Godric Smith. His laconic manner often contrasted unfavourably with Mr Smith's more emollient style and in his early days he appeared overwhelmed by the scale of the job, the confidence flooding back when he was asked a question about the minutiae of Ulster politics.
He was also caught out when Mr Blair's trip to Syrian backfired badly after his stance on Iraq was publicly criticised by President Bashar al-Assad. Mr Kelly failed to appreciate the extent of the public relations disaster as the Prime Minister had to endure a dressing down from his host, and did little to rebut the charges which rained down on Mr Blair.
However, over the past two years he has undeniably grown in stature as he shared the twice-daily briefings with Mr Smith, coping in the face of sustained assaults during the Jo Moore and "Cheriegate" controversies.
On the record, a deadpan delivery and a dogged adherence to a pre-prepared line have remained his defining features.
Off the record, he has become less robotic. But his determination to stick to this particular brief, the Walter Mitty line, may have sealed his fate.
TOM KELLY'S STATEMENT
The following is a full text of the statement issued yesterday by the Prime Minister's official spokesman, Tom Kelly, through No 10:
"Since the death of Dr David Kelly and the announcement of the Hutton inquiry, my public and private view has been that the family should be left to grieve and the inquiry to complete its investigation.
"Despite the continuing media focus on these issues and the many demands for briefings that we have faced, we have sought to keep briefing to a minimum in accordance with the Prime Minister's wishes.
"I deeply regret, therefore, that what I thought was a private conversation with a journalist last week has led to further public controversy. That was not my intention, nor, most emphatically, was I signalling a government strategy aimed at discrediting Dr Kelly.
"What I was trying to do, at the request of several journalists, was to outline the questions facing all parties that the Hutton inquiry would have to address, but to do so in a way that made it clear that it was for the inquiry to reach its judgment on the conflicting evidence before it, not me, or the Government.
"It was in that context that the phrase 'Walter Mitty' was used, but it was meant as one of several questions facing all parties, not as a definitive statement of my view, or that of the Government.
"We were discussing questions, not answers. I now recognise that even that limited form of communication was a mistake, given the current climate.
"I, therefore, unreservedly apologise to Dr Kelly's widow and her family for having intruded on their grief."