JK, two quotes - both taken from the current BBC website news report -
<< Up to 2,000 people are due at the Camp for Climate Action >>
<< About 1,800 officers from Surrey police, Thames Valley police, the Met, and British Transport Police will oversee the event. >>
From -
http://news.bbc.co.uk/1/hi/uk/6943549.stm
Appx one policeman (all armed with CS gas / batons / etc) for every man, woman and child !