Britain's historic Boat Race was dramatically disrupted Saturday when a wetsuit-clad protester swam across the River Thames, before Cambridge claimed a controversial victory over rivals Oxford.
The activist caused a half-hour hiatus in the race between England's two oldest universities, which is in now its 158th year, in a stunt that will raise security questions ahead of the Olympics and the queen's Diamond Jubilee.
After the race was restarted there was fresh chaos when the two crews clashed and one of Oxford's oars snapped off.
The team's desperate, abortive efforts to recover caused one of their rowers to collapse as they crossed the finish line, although Oxford boat race president Karl Hudspith later said he "is conscious and will hopefully be OK".
Hudspith condemned the protester who he blamed for Oxford's defeat, saying in a Twitter message: "My team went through seven months of hell, this was the culmination of our careers and you took it from us."
As he was pulled out of the water by a lifeboat crew, the swimmer appeared to have a broad smile on his face, before police arrested him on suspicion of a public order offence and took him into custody.
But the protest will raise questions about security ahead of an eventful summer in the British capital.
While rowing events for the 2012 London Olympics starting in July will be held at a closed course in Windsor, west of the city, a flotilla marking the queen's 60 years on the throne is set to proceed down the Thames in June.
British media identified the swimmer as an activist named Trenton Oldfield and published a statement he had purportedly posted on the Internet titled: "Elitism leads to tyranny."
"I am swimming into the boats in the hope I can stop them from completing the race and proposing the return of surprise tactics," he apparently wrote.
The two boats were about eight minutes into the race, with Oxford about a third of a length ahead, when the man wearing a black wetsuit swam in front of the two boats, and was nearly hit by the oars of the Oxford crew.
Spectator Mike Emerson said he had seen the man in his early 20s come through the trees on the south bank of the river and then get into the water long before the boats came past.
"He started swimming, he knew what he was doing," Emerson, who is 60 and from Cambridge, told AFP.
"He drifted down the river and then he waited near a pontoon until the boats came, and then he deliberately swam out toward the boats."
Umpire John Garrett halted the race after reserve umpire and former British Olympic rower Matthew Pinsent spotted something in the water.
"He (Pinsent) thought it was some debris and then we realised that it was actually a swimmer," Garrett said.
"We weren't sure what was going to happen, whether he was going to get out of the way in time and then it was quite clear he was just waiting for the boats to come across him, so I had to stop the race and restart."
It restarted around half an hour later but seconds after that the crews clashed and one of the Oxford oars snapped off, leaving them trailing far behind by the end of the race.
There was further drama after the finish when Oxford crew member Alex Woods, 27, collapsed in the boat and had to receive medical attention.
Coach Sean Bowden said: "I guess you can only imagine the desperation that Alex must have been in with only six crew-mates left and that's probably how he ended up pushing himself beyond his limits."
The traditional post-race presentation ceremony was abandoned.
"I think it's hard to imagine a Boat Race that contained so much to talk about," Pinsent told the BBC.
Umpire Garrett stood by his decision to award the win to Cambridge, saying the rules stated that crews "have to abide by their accidents".
"In the immediate run-up to the clash I was warning Oxford. Cambridge were in the right position so I was content to let the race continue and the result stand," he said.
The last time the Boat Race was restarted was in 2001 when the crews clashed and one of them lost an oar.
Once just an event for undergraduates at Oxford and Cambridge, the Boat Race has become an increasingly international event, with a succession of top-class rowers from around the world eager to take part.