Manchester City and Chelsea fans have packed out Wembley Stadium this afternoon as their teams clash for a place in the FA Cup final.
Police said they are investigating incidents involving Millwall supporters at today's FA Cup semi-final that left some fans bloodied and younger ones in tears.
A Scotland Yard spokesman said:
Millwall football fans fought each other at Wembley as their side lost 2-0 to Wigan in the FA Cup semi-final today.
Police intervened after MIllwall fans fought each other in the stands at Wembley as the London club lost 2-0 to Wigan Athletic in the FA Cup semi-final.
Former Millwall player Paul Ifill said Lions fans who fought each other in the stands during today's FA Cup defeat to Wigan "tainted the day".
Wigan Athletic have reached the FA Cup final for the first time in their history, beating Millwall in a match that was marred by scenes of violence involving fans of the London club.
Shaun Maloney and Callum McManaman scored in a 2-0 win for the Latics, whose victory means the club qualify for Europe.
Millwall fans could be seen fighting each other in the stands throughout the second half of the Wembley semi-final.
The winning crew finished in 17 minutes and 27 seconds to cut Cambridge's overall lead to 81-77.
Oxford have emerged as clear favourites to win the Boat Race after more than 70% of bets were placed on the Dark Blues, according to bookmaker William Hill.
Spokesman Joe Crilly said: "Oxford are certainly the best backed crew as of yet, although that was very much the case at this stage of proceedings last year.
"Last year, however, we took nearly £40,000 on the day of the race and Cambridge became best backed by the time the race started. Maybe history will repeat itself this time around."
Royal Marines will patrol the River Thames today to make sure there is no disruption to the Oxford and Cambridge Boat Race.
Organisers are trying to stop any repeat of last year when the annual race was stopped by Trenton Oldfield, who swam into the path of the crews.
The race's Executive Director, David Searle, said: "We are taking additional measures this year and have reviewed all of our actions last year in detail.
"The Boat Race course is four and a quarter miles long so we have eight and a half miles of riverbank to manage and monitor.
"What I would say to anybody thinking of disrupting the race is that it's unbelievably dangerous. You risk injuring yourself, the crews and the other people following the race.
"Nobody wants that to happen. This is just a sporting event."