By Danny Kemp

Britain's Olympic chief warned Sunday that security forces cannot rule out the threat of disruption to the London Games after a protester halted the historic Oxford and Cambridge Boat Race.

Australian activist Trenton Oldfield, 35, was charged with a public order offence after he caused a half-hour hiatus in Saturday's race by swimming in front of the two universities' boats in the River Thames.

British Olympic Association chairman Colin Moynihan said there was a high risk of similar incidents during the London Olympics, which begin on July 27, with the torch relay starting next month.

"It just takes, and is likely to be, one idiot. It's not likely to be a well-orchestrated campaign through Twitter or websites," Moynihan, himself a former Olympic rowing silver medallist, told BBC radio.

"It is likely to be someone similar to the idiot yesterday who causes major disruption. That is why all the security measures need to be put in place to minimise the chance of that happening.

"You can never completely remove it but you can do everything possible to protect the interests of the athletes by minimising it."

Moynihan said the British government and the London Olympic Organising Committee had been aware of the security challenges "since day one" and were looking at "every conceivable scenario".

"In many respects that is the biggest ask of the Games: you are not just talking about the competitions, you are talking about the pre-Games training camps, athletes will come well in advance based around the country, you've got the torch relay coming up, the public need to be protected.

"It's not impossible but it is a major challenge. You can never get it perfect unless you remove all the crowds and nobody is going to dream of doing anything like that."

A spokesman for Britain's interior ministry on Sunday said the government was "working to a robust and comprehensive safety and security strategy" and was determined to deliver "a safe and secure Olympic and Paralympic Games".

"We want to reassure everyone that we will leave nothing to chance in our aim to deliver a Games that London, the UK and the whole world will enjoy," added the official.

Oldfield's antics have also raised security fears for Queen Elizabeth II's Diamond Jubilee celebrations, during which a flotilla of 1,000 boats is due to travel down the Thames in June.

In a statement he posted on the Internet before the boat race incident -- that gave his motive for his actions as fighting elitism -- Oldfield urged other people to disrupt the Olympics.

"Are there events like today's boat race that you could do something similar to Emily Davison with?" he said, referring to a British woman's suffrage activist who was killed by a horse in a protest at the Epsom Derby in 1913.

"Is this possible in the lead up to and within the Olympics itself?"

Oldfield, who studied at the prestigious London School of Economics, has been bailed to appear in court on April 23.

Cambridge eventually won the 158th annual race between England's two oldest universities race but it was a controversial victory, with Oxford losing an oar shortly after it was restarted.

There was further drama when Oxford's bow oarsman, Alex Woods, collapsed in the boat just after crossing the finishing line.

Woods, 27, was discharged from hospital on Sunday, Oxford coach Sean Bowden said.

"He's on his way back home to Oxford. I think it was just a case of somebody being able to row themselves absolutely to a state of exhaustion," Bowden told BBC radio.

Photo AFP