The death came amid a series of protests in Britain's capital, involving about 4,000 demonstrators, a day before leaders of the G20 group of countries meet to discuss the global financial crisis.
While anti-capitalist protesters and those angry over the economic crisis converged on London's financial district on Wednesday, climate-change and anti-war activists gathered in other parts of the city.
Most of the demonstrations were peaceful, but some protesters smashed the windows of the offices of the Royal Bank of Scotland and wrote "thieves" on the side of the walls of the bank.
The bank, which has come to be seen as a symbol of everything wrong with the financial system, posted a $34bn loss last year, the worst ever in British corporate history, prompting a government takeover costing British taxpayers billions of dollars.
Other demonstrators threw fruit and eggs at police officers during the protests as riot police confined most of the activists to Threadneedle Street, next to the Bank of England, and at certain points pushed back against the protesters.
Police said a number of their officers were injured in the protests and added that there had been "a number of missiles thrown at officers and a number of surges at the police cordons, and increasing levels of violence towards police".
More than 30 people were arrested, with police mounting one of Britain's biggest security operations.
Demonstrators raised effigies of the "four horsemen of the apocalypse", representing war, climate chaos, financial crimes and homelessness.
Outside the Bank of England an effigy of a banker in a bowler hat hung from a traffic light.
Michael Rainsvro, a protester from the G20 Alternative movement, told Al Jazeera that the demonstrators outside the Bank of England wanted a "real dialogue" about the world's economic future.
"We are seeing 20 men in a room making decisions for the 20 richest countries in the world, but these decisions effect the entire world," he said.
"We came to the central bank of England to say: this is not just a problem with a few regulators and a few bad bankers, this is a problem that has been going on for years."
More protests planned
Shop fronts and restaurants were boarded up to protect them from the protests, and helicopters hovered over the demonstrations.
"I am angry at the hubris of the government, the hubris of the bankers," Jean Noble, one of the protesters, said.
"I am here on behalf of the poor, those who are not going to now get their pension or who have lost their houses while these fat cats keep their bonuses, hide their money in tax havens and go and live where nobody can touch them."
A smaller demonstration against Britain's military role in Iraq and Afghanistan attracted several hundred people in Trafalgar Square.
Protesters have planned another day of action on Thursday to coincide with the opening of the summit.
The meeting of world leaders is expected to focus on how to deal with the global recession, the worst in 80 years.