The Prime Minister met some of the world's most influential and powerful people, but we will not be told who he spoke to, nor what they discussed.
David Cameron was attending the annual meeting of the secretive Bilderberg club. The group insists on total privacy so members can talk candidly about global issues.
But, as Political Correspondent Carl Dinnen reports, there's growing anger at its lack of openness:
Downing Street has denied that the Prime Minister's decision to attend a private meeting of the secretive Bilderberg Group today ran counter to his promise to lead the most transparent government ever. A spokesman said:
The Prime Minister is to attend a private meeting of the secretive Bilderberg group later today, Downing Street has announced.
The international group of politicians, business leaders and academics is holding its annual conference behind closed doors at a luxury country hotel near Watford.
A Downing Street spokesman said: "My understanding is that it is usual for Bilderberg to invite the head of government of the country where it is meeting. He will participate in a discussion around domestic and global economic issues.
"He feels it is an opportunity to discuss economic issues with senior ministers, businesspeople and academics".
Labour MP Michael Meacher has spoken out against the "secrecy" of the Bilderberg summit.
Mr Meacher, 73, called the delegates the "real top brass of western finance capitalism" and insisted that they should be held accountable.
"My objection is that it's being done in utter secrecy with the police keeping everyone else out."
Speaking in the protest area, the MP said the sheer volume of leaders and influential people at the conference means they should be held accountable.
"When 130 of the leaders from all across the West get together, and many of these are billionaires, they are people who are immensely wealthy and immensely powerful
"And when they all get together, it's not just to have a chat about the latest problem, it is to concert plans for the future of capitalism in the West.
"That is on a very different scale."
Delegates for a private conference of top politicians and businesspeople from around the world have started to arrive at a luxury country hotel in Herefordshire.
Several cars with blacked-out windows entered the gates of the Grove Hotel, near Watford, this morning for the secretive meeting of the Bilderberg Group.
It is thought executives from multi-national companies such as Amazon and Google, and high-ranking political figures including Chancellor George Osborne will be among the 130 or so attendees.
Members of royal families are also expected to attend the meeting
Amid tight security, a handful of protesters gathered in a fenced-off area just inside the grounds of the hotel and heckled cars as they drove past.