The father of golf champion Rory McIlroy is set for a massive payday after his son won the British Open today.

Gerry McIlroy and three friends each placed a bet of £100 ($182) 10 years ago that Rory, now 25, would win the British Open before he turned 26, according to a ninemsn report.

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The incredible bet will see him pocket £200,000 (A$363,798), while Rory McIlroy will walk away with $1.66 million in prize money.

Gerry McIlroy was once a golfer himself, and has coached his son since a young age.

The North Irish golfer now enters an elite group of only a handful of golfers to win three grand slams before turning 26.