London 2012 Olympics: Boat Race protest swimmer Trenton Oldfield 'serves as a reminder of Olympic Games threat' In events such as the open water swimming in Hyde Park as well as the marathon, triathlon and road cycling, the public will line the route. Moynihan, a former Olympic rowing silver medallist, admits the threat can not be eradicated but insists security is constantly under review. He told BBC Five Live's Sportsweek programme: "It just takes, and is likely to be, one idiot. It's not likely to be a well-orchestrated campaign through Twitter or websites. 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. He added: "It is so important to work closely with police and security agencies and to put in place every possible measure to protect the interests of all the athletes. 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 is a major challenge and the Government have been aware of this since day one and work closely with LOCOG (the Olympic organising committee). Every conceivable scenario is being reviewed and I'm confident no more can be done. 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. Moynihan also expressed sympathy for the two Boat Race crews in a race won by Cambridge, after Oxford lost an oar, while a member of the Oxford crew was taken to hospital after collapsing in his boat. "These guys train for seven months, day in, day out, it's their sporting event because it is just one race, you don't have a whole season to look forward to," Moynihan said. For it to be effectively destroyed as it was yesterday by the actions of a crazy guy who was hugely putting his life at risk - not just from the blades from the crews but from the flotilla behind was just to me a massive disappointment. Trenton Oldfield is escorted from the Thames by police officers. Four-time Olympic rowing champion Matthew Pinsent was looking up the river as part of his role as assistant umpire yesterday and spotted something in the water. He said: "The first time I saw the head in the water I thought it was the balloon floating on the water and then I saw an arm coming up and I could tell it was someone swimming. Absolutely no hesitation from (umpire) John Garrett once it was a swimmer and it was obvious he was swimming into the crews and not away from them - you've got no alternative but to stop the race. It could have been a lethal situation.