Rory McIlroy ended his season by winning the $8 million DP World Tour Championship – his fourth title of the year – on Sunday and retained his Race to Dubai crown to become the European number one for second straight year.

The world number three had to battle hard and then get over a errant tee shot on the 17th hole that ended in the water to beat overnight leader Andy Sullivan of England, who fought tooth and nail and forced McIlroy to dig deep.

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The win was worth $3.208 million (3.02m euros for McIlroy – $1.33 million for winning the DP World Tour Championship and $1.875 million bonus for winning the Race to Dubai.

McIlroy, who will remain the world number three behind Jason Day and Jordan Spieth despite the win, finished on 21-under par 267 for the tournament.

That was one shot better than Sullivan, who added a second successive 68 over the weekend to finish on 20-under par 268.

By winning the tournament, the Northern Irish star made sure none of the permutations needed to be worked against the six other players in the reckoning for the Race to Dubai crown could work.

England’s Danny Willett (70) gave it his all, but ran out of the holes towards the end and two late bogeys meant he finished tied for the fourth place at 13-under par 275.

South Africa’s Branden Grace made a five-under par 67 to finish alone in third place at 15-under par 273.

After trailing Sullivan for most part of the day, McIlroy built a two-shot lead over the world number 53, who was looking for his fourth win of the season on the European Tour, with back-to-back birdies on the 14th and 15th holes.

But after the leading group was made to wait on the 17th hole, McIlroy failed to draw his tee shot and splashed into the water.

He pitched to nearly 40 feet from the cup and with Sullivan making a regulation par, a two-shot swing looked imminent.

However, McIlroy made what he called the ‘best bogey of his life’ to limit the damage to one shot, and secured the win with a par on the 18th.

The deficit was down to one after eight holes and McIlroy could have made the turn tied for the lead if not for a stunning chip-in for par from behind the ninth green by Sullivan.

On the back nine, McIlroy finally caught up with Sullivan with back-to-back birdies on the 11th and 12th holes

Korea’s Byeong-hun An won the Sir Henry Cotton Rookie of the Year award on the European Tour by finishing ahead of his closest challenger Matthew Fitzpatrick of England in the Race to Dubai.

The BMW PGA Championship winner however closed with a 71 and finished tied with the British Masters champion at 13-under par 275 and joint fourth.

Englishman Justin Rose, the world number five, went 12 shots better than his third-round 78 to close the year with a 66 that improved him to seven-under par 281.