On an historic day's golf in the game's oldest championship, South Africa's Branden Grace made history when he shot the first 62 in a major but the day still belonged to 23-year-old Spieth, whose five-under-par 65 was his third consecutive round in the 60s and gives him a three-shot lead over compatriot Matt Kuchar going into Sunday's final round.

Spieth will take the memory of his Augusta National meltdown at the 2016 Masters into Sunday's final round, when he had led by one overnight then opened up a five-shot lead only to quadruple bogey the par-three 12th and hand victory to England's Danny Willett.

“I think I am in a position where it can be very advantageous,” Spieth said of that experience on Saturday night, “everything I have gone through, the good bad and everything in the middle.

“I understand leads can be squandered quickly and I also understand how you can continue to build on one. So, it was a humbling experience that I thought at the time could serve me well going forward.”

Bogey-free Spieth and Kuchar, whose 66 sent him to eight under par separated themselves from the rest of the field with US Open champion Brooks Koepka and Canadian 20-year-old Austin Connelly the best of the rest on five under for the tournament following rounds of 68 and 66 respectively. Grace's eight-under 62 lifted him four under in a tie for fifth with Japan's Hideki Matsuyama but despite a blistering start of three birdies in his first five holes, McIlroy could not sustain his charge and as his putter went cold, the Irishman slipped back to two under par with a third-round 69 that leaves him nine shots off the leader.

The four-time major champion had started the day at one under par, five shots off the pace set by halfway leader Spieth and birdied the first, fourth and fifth holes to indicate he was primed for a serious charge towards the top of the leaderboard.

In truth, though, McIlroy had missed a gilt-edged chance to eagle the fifth, the shortest of Birkdale's par fours with the tee moved up to just 287 yards. He had driven the green with an excellent tee shot to 12 feet but left his eagle putt short, settling for a tap-in birdie to move to four under that was the closest he came to closing the gap.

Back-to-back bogeys at the seventh and eighth were followed by a bounce-back birdie at the ninth but disaster struck at the 10th, where McIlroy under-clubbed off the tee and found a bunker, costing him dearly as he double-bogeyed to fall to one under, eight adrift of Spieth.

Birdie opportunities came and went on the back nine as McIlroy failed to capitalise on the two par-five holes, holing a birdie at 15 that was another eagle chance and only parring the 17th.

On the face of it, even making the halfway cut was an achievement for McIlroy after three missed cuts in his last four starts following his return from a rib injury but the Holywood star said: “It's hard to think big picture now, I'm just off the golf course and I'm a little disappointed.

“This week has been a step in the right direction, there's no doubt about it. And I need to pick myself up, play a good round tomorrow and hope for some bad weather. And hope for some guys to struggle. And we'll see what happens. Yeah, I definitely feel like today was an opportunity lost to get right in the mix going into tomorrow.”

Spieth, however, does not look in the mood or the form to let any bad weather derail his march to a third major title following his back-to-back triumphs at the 2015 Masters and US Open. The world number three had won those having shot consecutive first and second rounds in the 60s and the Texan continued his equally strong start to this week's campaign with another convincing performance as he duelled in the final pairing with Kuchar.

Any move made by Kuchar, 39, was matched by his younger rival, as both Americans went out in 31, three under par, Spieth maintaining his two-shot cushion until the par-three 14th, where the gap was closed to a stroke with a Kuchar birdie. Both men birdied the par-five 15th but then Kuchar double-bogeyed the par-four 16th and there was a three-shot swing in Spieth's favour. Kuchar clawed a shot back with birdie at 17 but Spieth regained a three-shot cushion at the last, rolling in an imperious putt from 24 feet to have an emphatic final say on a gripping third round.

It looks like a battle for the minor places on Sunday with world number one Dustin Johnson a shot behind Matsuyama and Grace on three under after carding a six-under 64 to move into a tie for seventh with defending champion Henrik Stenson, who posted a 65, Korea's Chan Kim (67) and Spain's Rafa Cabrera Bello (67).

They are in turn a shot ahead of a British and Irish quartet on two under featuring McIlroy, Englishmen Ross Fisher (66) and Ian Poulter (71) and Scotland's Richie Ramsay (70).