Rory McIlroy took £20 off Darren Clarke in a practice round bet

Gambling is a crucial part of any friendly round of golf, so when Rory McIlroy and Darren Clarke played their practice round together at Royal Liverpool, they decided to make things interesting. Clarke ended up forking over £20, and the BBC was there to capture it on film.

Clarke and McIlroy will have to get their gambling done before Thursday, though. According to ESPN.com, officials at this week's Open Championship are requiring players to sign a waiver saying they will not bet on the tournament. Sports betting is not only legal in Britain, it's quite prevalent. ESPN.com quotes one anonymous player representative as saying there are probably "at least 30 guys" who have already placed bets on the action. 

If he's willing to break the rules (and if he manages to win), Clarke could make his money back (and then some) by betting on himself. The 2011 Open champion is at 250/1 odds, according to VegasInsider.com. McIlroy is listed at 15/1, but Clarke might be the better bet—he won the Open the last time he played his practice round with McIlroy. McIlroy, though, could make his father and a few friends rich with a win at Hoylake. When Rory was 15, his father and three friends bet £100 each that Rory would win the British Open by 2014. If he does, the bet pays £200,000.

- Dan Gartland