Police intelligence obtained by monitoring chatrooms and e-mails indicates that some anarchists want to make trouble on what is dubbed "financial fools' day," which falls on April 1 and April 2, by instigating anger at the ever-deepening financial crisis.

O'Brien said police will not only have to ensure safety at the summit venue in east London, but also at the hotels the leaders are staying while at the same time dealing with protesters, some of whom want to "stop the city".

Access to the summit venue will be severely restricted. There will be enough barriers and police check points, O'Brien said, to practically make the site "a ring of steel".

From March 24 to the end of the summit, 10,500 police duty shifts will have been deployed, some coming from outside London for specialist functions, the Met commander said.

So far, police has received seven protest requests including young people rallying against job markets. O'Brien urged all those planning protests to contact police so they could help facilitate the event.

"People have the right to freedom of speech. However, we won't tolerate unlawful behavior such as attacking buildings or other people," he said.

Police costs for the G20 summit will be around 8 million pounds, making the operation the "most expensive" in British history.

Normally, there are 35,000 police officers in London. On April 1 and 2, all police leaves have been cancelled. Thousands of officers will patrol the streets, with armed plain-clothes police officers mixed among commuters. Snipers will be positioned on higher buildings. The Stansted Airport to the northeast of London and a nearby military base will be on standby for world leaders to land. Contingency plans also are ready for the summit venue to move in case of any disruption.

Up to now, there has been no police intelligence of any terrorist attacks and the country's alert level remains "severe". "We have taken into consideration more potential threats from protests," O'Brien said.

(Xinhua News Agency April 1, 2009)