Jean-Paul Carbonnier, a journalist, was at the International Petroleum Exchange in London for a meeting with Instinet, a Reuters company that is housed in the same building close to Tower Bridge.

"I arrived about 2pm for the meeting and saw dozens of Greenpeace activists lying on the floor of the exchange. They were surrounded by security guards as well as the traders, wearing their distinctive coloured jackets.

"Many of the traders were not in the least bit impressed with the invasion and some told the activists to 'get the f*** out'.

"The Greenpeace supporters came armed with whistles, foghorns and other noise-making devices. Every so often someone would let off a foghorn before a security guard would attempt to wrestle it away.

"Things did get a bit heated at times and there was some measure of physical violence. I saw a couple of people being grabbed by the neck or even all four limbs and dragged out of the building. The entrance was sealed off by dozens of police who descended on the scene.

"It was somewhat bizarre seeing two groups from society who would never otherwise have anything to do with each other in such close quarters. Clearly the traders would rather have been getting on with the business of making money, but the activists seemed to be enjoying the disruption they were causing.

"While the physical trading stopped, the exchange also has electronic trading and that continued oblivious to the events. I think the protest was misdirected - the United States, which has not signed up to the Kyoto Treaty, produces twice as much carbon dioxide as Europe."

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