The Metropolitan Police launched a security review at the Houses of Parliament after two anti-war protesters scaled the Big Ben clock tower yesterday.
Officers had to wait seven hours until brothers Harry and Simon Westaway, who are both members of Greenpeace, ended their demonstration. The pair were arrested on suspicion of causing criminal damage.
The protesters, aged 26 and 24, from Lewes in Sussex, climbed the landmark after climbing over a wall and a security fence. They were taken to a central London police station for questioning.
The stunt was described as a "dangerous embarrassment" by MPs, especially when Britain is on a heightened state of alert against possible terror attacks. David Blunkett, the Home Secretary, is expected to receive a police report into the incident early this week.
Greenpeace said it had been "easy" for the pair to breach security. Keith Simpson, the shadow defence spokesman, said it was a "wake-up call" for security.
"This is a dangerous embarrassment for Parliament and the police, which we expect to be fully investigated," he said.
"We can't turn Parliament into a complete fortress, or the terrorists will have won, but we have to put in place a credible security system to deter terrorists, and this means that MPs will have to play their full part."
Mark Oaten, the Liberal Democrat home affairs spokesman, said the incident raised "obvious" security questions.
"More alarmingly, what would have happened if these people were terrorists rather than peace protesters?" he said.
The two Greenpeace protesters, both experienced climbers, began their protest around 6.15am yesterday. They reached the clock face of the 315ft tower, where they planned to unveil a large banner saying "Time for the truth", referring to claims that Tony Blair misled Parliament over the war. But strong winds meant they could only display smaller cards, and they ended the protest just before 1pm.
Deputy Assistant Commissioner Brian Paddick, who is in charge of territorial policing for the Met, said the men would have been unable to gain access to the House of Commons but could have left something by the wall and run off had they been terrorists.
"They got inside the first perimeter, but they did not get anywhere near any offices of importance," he said.
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