Oxford won its fifth Boat Race in seven years on the River Thames on Sunday after an early clash of oars damaged university rival Cambridge's hopes of victory.

Oxford finished 11 lengths ahead, the biggest winning margin since 1973, and completed the 4-mile course in 18 minutes, 36 seconds.

Looking for its first victory in the annual event since 2012, the Cambridge crew had an aggressive start. However, the 160th race was effectively over after just five minutes when the Light Blues' two-seat Luke Juckett of the United States slipped from his position, allowing Oxford to pull clear after the boats appeared to have got too close.

''It happened in a split second,'' Juckett said. ''That definitely didn't help.''

Juckett almost went overboard before regaining his balance but his team lost precious time and never recovered. Cambridge immediately lodged a protest after reaching the finish in Mortlake but umpire Richard Phelps dismissed their complaint.

''I think the Cambridge appeal was that, when the contact occurred, Oxford were not on their proper station and therefore Cambridge were victims of an illegal foul from Oxford,'' Phelps said. ''From my perspective, Oxford were on their proper station quite clearly, so for there to have been contact it could have only been on neutral water or, at the worst, Cambridge being off their station.''

Cambridge still leads the series 81-78, with one tie. The race between the universities first took place in 1829 and is one of the oldest sporting events in the world.

Oxford cox Laurence Harvey was thrown into the river by his teammates after the finish while the Cambridge crew tried to regroup on the bank of the river.

''After the collision I saw Luke's blade come into my field of vision,'' Cambridge president Steve Dudek said. ''It's a very frustrating way to lose but, as a group of men, I couldn't be happier with the way they handled today. This is a phenomenal group of men and the only thing I would change is the result.''

The Dark Blues won the toss and decided to start from the Surrey Station, the south bank of the Thames. Cambridge had a weight advantage of 5 kilograms a man over their rivals but it did not prove decisive.

The race started in mild but overcast weather and the crews almost clashed immediately, fighting for the fastest water and setting a quick pace. While Oxford was the pre-race favorite, the event looked poised for a tight battle until the clash of blades killed off any sense of suspense.

Oxford's stroke Constantine Louloudis managed a hat trick of victories after winning in 2011 and 2013, taking a break in 2012 to focus on the Olympics.

''We had a plan and we stuck to it. I think we showed that, with the distance, we had control of the race,'' Louloudis said.

Over the years, the race has been marred by incidents. In 2012, the event was halted after a man swum in front of the boats when the two crews were side by side.