More than 100 people who tried to prevent weapons companies from setting up stalls at the world’s biggest arms fair have been arrested.
Scotland Yard said 102 people who tried to stop the the event from going ahead were arrested, mostly for blocking traffic trying to reach the centre.
The Government has been accused of double standards for participating in arms control talks in Geneva at the same time that London hosts the arms fair.
The opening on Monday coincides with the annual meeting of signatories to the Arms Trade Treaty in Switzerland.
The UK has been criticised by Oxfam for selling arms that fuel the war in Yemen, while also funding aid efforts to help those suffering.
Sally Copley, Oxfam GB’s head of campaigns said: “Yemen is the world’s worst humanitarian crisis, suffering from a borderline famine and hit by the world’s largest cholera epidemic which shows no sign of abating.
“Yet the deaths, the destruction and the misery seem to count for nothing.
“Since the war began not one licence to export arms to Saudi Arabia has been rejected by the Government.
“When you are witness to the suffering in Yemen it is hard to understand or excuse how the UK government talks the talk on arms control while it walks the walk of arms sales.”
She added that this was most apparent in the case of £3.6 billion worth of arms sales to Saudi Arabia for its bombing campaign in Yemen.
“On the one hand it fuels a war with massive arms sales while it sends aid to help the people it is harming,” she said.
“Our call to the Government is clear: Britain’s reputation on the global stage demands that you stop being an arms broker and start being a peace broker.”
Meanwhile Jeremy Corbyn also called for the UK to stop arms sales to Saudi Arabia amid concerns they are fuelling the bloody civil war in Yemen.
The Labour leader said Britain was exporting “far too many” arms to countries which abused human rights and that the time had come to “do something about it”.
Mr Corbyn told BBC Radio 4’s The World at One: “We are selling arms to Saudi Arabia.
“Those arms are being dropped on Yemen. At the same time, we are sending aid in from the Department for International Development.
“We should not be doing both. We should be sending aid in and ensuring there is a political process to bring about a ceasefire and bring about a longer-term political settlement.”
A spokesman for the Department of International Trade said: “The UK government takes its defence export responsibilities very seriously and already operates one of the most robust export control regimes in the world.
“We rigorously examine every application on a case-by-case basis against the Consolidated EU and National arms export licensing Criteria.
“The Government undertakes a stringent process of scrutiny and approval before issuing any invitations to foreign governments to attend a major UK defence exhibition like DSEI.
“Respect for human rights is a mandatory consideration in the process and a country would not be invited where that would contradict the UK’s international obligations.”