Downing Street laughed off an attempt by a climate-change protester to superglue himself to Gordon Brown.
Activist Dan Glass had been attending an event in Number 10 to recognise the contribution of the voluntary sector when he staged the demonstration.
As he was about to shake hands with the Prime Minister, Mr Glass - a member of campaigning group Plane Stupid - tried to attach himself to his suit.
At the same time, he demanded to know why the Government was ignoring objections to building a third runway at Heathrow airport.
Whitehall sources insisted the bid had been unsuccessful and there had never been any threat to Mr Brown.
Police sources also stressed they did not believe there had been any security breach, because Mr Glass was invited and did not cause any damage. The 24-year-old has not been arrested.
A Downing Street spokesman said: "As far as we are concerned, nothing really happened.
"There was a light-hearted and not particularly successful demonstration at a reception that was being hosted at Downing Street."
Mr Glass, 24, from Barnet, north London, was given a round of applause by the audience as he urged the PM to change his mind on Heathrow expansion, he said.
Speaking afterwards, he said Mr Brown grinned at him and then pulled his hand away when he realised it was stuck.
