The City prepares for this week's G20 protests

Live footage from CCTV is shown on a large screen in the Metropolitan police specialist operations room in Lambeth, south London. Police will have access to more than 3,000 cameras as the world's most powerful political leaders arrive in London for Thursday's G20 summit Photograph: Anthony Devlin/PA

A police search team carry out checks near the ExCeL centre Photograph: Matt Dunham/AP

A tailor's shop is boarded up near the Bank of England in central London Photograph: Carl De Souza/AFP/Getty Images

An armed police officer passes the front of 10 Downing Street Photograph: Toby Melville/Reuters

Armed police patrol the Mall in London Photograph: Adrian Dennis/AFP/Getty Images

Shops around the Bank of England are boarded up in case the G20 protests get out of hand Photograph: Dan Kitwood/Getty Images

The ExCeL exhibition and conference centre which will host the G20 summit Photograph: Stefan Wermuth/Reuters

Demonstrators against the G20 gather to have a cup of tea in front of the Bank of England. Photograph: Akira Suemori/AP

A man is stopped and searched by police outside the Bank of England, while a woman passing by is warned off Photograph: Ray Tang /Rex Features

A man protests about capitalism outside the Bank of England Photograph: Dan Kitwood/Getty Images

Council workmen remove bins and other potential projectiles from the pavement in front of the the Bank of England Photograph: Ian Langsdon/EPA

Mounted police officers patrol in front of the Bank of England Photograph: Ian Langsdon/EPA

Police officers on duty near the ExCeL centre in London's Docklands Photograph: Stefan Wermuth/Reuters

Workmen board up a statue in Trafalgar Square in preparation for the G20 protests Photograph: Jeff J Mitchell/Getty Images