A protester who swam into the Thames to disrupt this year's Boat Race could have been killed, four-time Olympic gold medal rower Sir Matthew Pinsent told a court.
Sir Matthew, who was assistant umpire during April's race, made a written statement to police just hours after Trenton Oldfield, 36, was plucked from the path of the speeding Cambridge and Oxford boats.
Oldfield, of Myrdle Street, east London, denies causing a public nuisance but admits swimming in the path of the crews.
Trenton Oldfield denies causing a public nuisance during the Oxford-Cambridge boat race
Isleworth Crown Court heard on Tuesday that Sir Matthew was immediately behind the university crews on a launch with umpire John Garrett.
Behind them were another 25 motorised boats with officials, police, sponsors and camera crews.
Half way through the four-and-a-quarter mile race Sir Matthew, whose job was to look ahead of the crews, saw what he thought was a balloon in the water.
He told Mr Garrett there was debris in the water ahead.
But as they got closer Sir Matthew realised it was a swimmer who had chosen to swim into the path of the boats, he said.
In a statement read by prosecution barrister, Louis Mably, he said: "The risk for the swimmer was great, he could have been killed if he had been struck by an oar or the rigging which is metal. The incident caused me alarm as one of my primary roles is the safety of the competitors and public at large.
"I was worried about the safety of the swimmer.
"If he had been hit by an oar or boat he could have cracked his skull, his neck, fallen unconscious and drowned."
Sir Matthew has previously competed in three of the university boat races and acted as an official in four.
Trenton Oldfield could have been killed, four-time Olympic gold medal rower Sir Matthew Pinsent told the court
Mr Garrett agreed the defendant could have been killed by the boats which were travelling at about 20mph.
"I think he put his life at risk doing what he was doing," said Mr Garrett, who halted the race waving a red flag and using a megaphone.
"He put himself in very high danger and it wasn't just himself he was putting in danger.
"With so much traffic following on that tide there was a risk there may have been crashes between some of the boats."
Mr Garrett said there had been warnings of swimmers the previous year but nothing ahead of 2012's competition which Cambridge eventually won after a restart.
The court heard that the wetsuit-cladded Oldfield, an Australian, had folded his clothes in a neat pile before entering the water.
Spectators Andrew Mann and Debra Bailey had arrived in Barnes between the Hammersmith and Barnes bridges before the race where the engaged couple came across Oldfield.
Watch the moment Oldfield disrupted the Boat Race...
They talked to the defendant who told them: "I just want to be quiet," said Mr Mann in a prosecution statement.
The witness said the pair later recognised Oldfield when they saw him in the water.
After being removed from the river Oldfield was seen grinning and waving, the court heard.
He was put on an RNLI boat without a police presence.
A nearby off-duty officer, chief inspector Vincent Hall, who was watching the race, realised there was a potential danger to him from an increasingly angry crowd so boarded the boat and arrested him to prevent a breach of the peace.
Asked why he had entered the water, the officer said Oldfield told him: "To protest against elitism."
Officers from the police marine unit arrived and Oldfield was taken into some nearby toilets "because of the animosity against him from the crowd", prosecuting counsel said.
The eight women and four men of the jury heard that Oldfield faced boos from the crowd who verbally abused him and were aggressive.
When he was taken to the police station to be questioned, officers found Oldfield had a solicitor's telephone number written on his arm, the court heard, and it was claimed he said: "I did plan this."
Entering the witness box, Oldfield said some spectators thought his actions had improved the race.
"Lots of people thought it made it the most exciting boat race ever," he said.
Mr Mably drew laughter from the room responding: "Oh, were the crowd coming up to you slapping you on the back saying good job, Mr Oldfield, well done?"
"No," he answered, adding: "I don't think I will be willing to rock the boat next year."
Oldfield said he returned from Canada days before the race on April 7 annoyed by Government plans to "sell-off" the NHS, "snoop" on electronic communications and by encouragement given to "dob in" people planning protests during the Olympics.
Saying that London "has the highest inequality in the western world," Oldfield said the Boat Race was a symbol of elitism in Government.
Asked what the Boat Race had to do with it, he said: "It's a symbol of a lot of issues in Britain around class, 70% of Government pushing through very significant cuts are Oxford or Cambridge graduates.
"It was a symbolic gesture to these kind of issues."
Oldfield, who moved to the United Kingdom in 2001, said he had worked and volunteered for a decade working in jobs and projects aimed at increasing better prospects for people in impoverished areas.
With coalition public spending cuts implemented London was "kind of worse than in Dickens' time", he said.
"With these levels of cuts it became apparent to me that something needed to be done.
"I felt it was an important thing to do."
Oldfield rejected the idea he could have been hurt by the boats.
He insisted, repeatedly stating that "having grown up in Australia", he was well used to avoiding surf boards, boats, rocks and coral while swimming.
He told the court he could have ducked under any of the boats on the Thames.
"It's not called wild swimming, just swimming," he said.
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