The world number two carded a hat-trick of birdies from the fourth to reach the turn in 32 and also birdied the 10th before a costly bogey on the 12th, but responded with three more birdies in succession and picked up another shot on the 17th.

An eagle on the 18th would have given the leaders something to think about but the 26-year-old failed to find the fairway off the tee and had to settle for a par five.

That left McIlroy two behind former Walker Cup team-mate Willett, who lost his overnight lead after a bogey on the second but found himself three in front thanks to three birdies in four holes from the fourth.

A bogey on the ninth allowed the chasing pack to close the gap, with fellow Englishman Andy Sullivan carding his third birdie of the day on the ninth to get within a shot, with Rafael Cabrera-Bello, Alvaro Quiros and Byeong Hun An alongside McIlroy on 15 under.

Willett saved par from a greenside bunker on the 11th and then doubled his lead on the next, holing from five feet for birdie on one of the hardest holes on the course.

McIlroy’s title defence had officially come to an end when Quiros birdied the 18th to complete a flawless 65 and finish 16 under, a score and total soon matched by An, the 2015 European Tour rookie of the year.

Cabrera-Bello produced an excellent birdie on the par-five 13th after driving into the trees to join the group on 16 under, but playing partner Willett birdied the same hole to extend his lead to three with five holes remaining.

The gap was suddenly cut to a single shot when Sullivan produced a superb tee shot on the 15th to set up a birdie and Willett three-putted from just short of the green on the 14th.

And Sullivan then crucially saved par on the 16th after hitting a wild drive into the trees, the world number 37 holing from 18 feet and celebrating with an exuberant fist-pump.

Cabrera-Bello closed to within a shot of the lead with a birdie from close range on the 17th before Sullivan birdied the last from 10 feet to join Willett on 18 under.