Thousands gather for G20 protests

Campaigners waving flags and placards braved wet weather to take part in the Put People First march, which comes amid anger at the £19 million cost of staging the conference at a time of economic downturn.

The march featured an alliance of 150 groups, including unions, charities, environmental campaigners and faith organisations.

A massive police operation was launched as officers warned of an "unprecedented" threat posed by the protests, but the organisers stressed the events would not turn violent.

Climate Change Secretary Ed Miliband met campaigners before the march got under way and said the "vast majority" were planning peaceful protest.

TUC General Secretary Brendan Barber, who was due to lead speeches at the rally, told the BBC Radio 4 Today programme: "If there are other groups who want to cause trouble, I don't want to see them anywhere near our event.

"I read about other events being planned by other groups over the next couple of days. If people want to make their protest in other ways, not the peaceful ways that we are absolutely committed to, then they should go in other directions."

The Bishop of London, Richard Chartres, said the atmosphere at the event was "positive", adding that it would be a "tragedy" if events turned violent.

He told Sky News: "It's not ideal weather for a demo this morning but nevertheless the atmosphere here is very positive indeed."