With 188 years of history and only two teams in it, the Oxford and Cambridge University Boat Race is one of the longest and most bitter rivalries in sport.
But the tension between the two crews has intensified this year after one of their number committed the cardinal sin of switching sides.
Now the rowers, and their fans along the banks of the River Thames, are anticipating even greater levels of animosity, both off and on the water, following William Warr’s defection from the light blue of Cambridge to the dark blue of Oxford.
Mr Warr is bracing himself for greater than normal levels of hostility when he appears alongside his crew mates at Putney for the start of Sunday's 4.2 mile race to Mortlake.
“I’m sure people will have different opinions about what I’ve done and maybe there will be slightly more ‘talk’ about the race this year because of it,” he told The Telegraph.
In 2015 Mr Warr pulled alongside his Cambridge crewmates, losing by six lengths, but this year he switched to their rivals after transferring to Oxford University to do his PHD in public health policy.
In an attempt to soothe the troubled waters he wrote a message explaining his decision to Ben Ruble, his once-close friend on the Cambridge crew.
But the only response he received was frosty silence.
“I’ve not received a reply from him,” Mr Warr said, admitting he was disappointed with his rival’s lack of magnanimity.
However, he added, perhaps in a spirit of reconciliation: “But it’s the week of the race and both crews are focusing on their performance. We are all just concentrating on the race.”
Mr Ruble declined to comment on how he felt about his former crewmate’s defection.
Warr will today become only the third man to race for both crews, an achievement which would be lauded in any other sphere. Not in the world of the boat race.
“There’s definitely some ill-feeling there. Which is hard, because I was very close to these guys. And I don’t really speak to half of them at all now,” he said. “It was probably the toughest decision I’ve ever made.”
Mr Warr spent a year as an advisor to the Conservative MP Jessica Lee, and now does occasional work for the political strategist Sir Lynton Crosby.
He says he “would not rule out” going into politics in the future, but for the moment he is concentrating on getting into the British team for the Tokyo Olympics.
Should he succeed he may well, given the way sport works, find himself alongside some of his bitter rivals from the Boat Race.
But Mr Warr has no regrets over switching sides.
“I wanted to do a particular PhD, I want to go to the 2020 Olympics, and the only way of doing them both was to row at Oxford,” he said.
In 1985 Bruce Philp became the first man to row for both universities, after representing Cambridge in the 1982 and 1983 races. Having twice lost with Cambridge he won with Oxford.
Richard Young , who had rowed for Cambridge when they lost the 1990 race, switched to Oxford the following year. Oxford won.
No wonder the light blues don’t like splitters.
“Both clubs build up this intense hatred,” said Warr. “You’re just brainwashed to hate Cambridge, or hate Oxford. There’s a reasoning behind it: it’s a very easy way to get a squad of guys to bond quickly. But actually, they’re very similar clubs. Very similar kinds of people, very academically motivated.
“The structures of the programmes are pretty similar. You train at similar times, you put similar hours in. And I think if people took a step back, they would realise that actually, the guys they’re racing could easily be very good friends.”