The £27m G20 security operation
Updated on 31 March 2009
Senior police officers have described it as "unprecedented". As world leaders begin arriving in London, among them the new US president Barack Obama
Leaders from the world's leading economies will discuss measures to tackle the global recession.
But the summit is also expected to attract thousands of protesters.
Alex Thomson talks to Mel Evans, a protester from Camp for Climate Action.
Click here to view a map of the planned G20 protests.
Channel 4 News talks to Brendan Barber, the general secretary of the Trades Union Congress.
