Having commenced early on day three to avoid the predicted storm, the conditions could not have been more conducive to low scoring. With little, if any, breeze, the Royal Liverpool layout was vulnerable and early on the scoring confirmed just that.
As the leader tread water through the opening nine holes after a bogey at the first, the field began to close in.
McIlroy's stunning finish however, which included eagles at the 16th and 18th, re-established and in fact increased his considerable lead after he had been challenged at various stages during round three.
The 25 year old now leads by six over Rickie Fowler and by seven over Sergio Garcia and Dustin Johnson, seemingly on track for his third major title and if he is able to go on with it tomorrow then all three of them would have been won by huge margins.
Day three however was not as comfortable as the leader-board now suggests for the Northern Irishman. The perfect conditions for scoring provided the opportunity for an all-out attack by his chasers and first Johnson and then Fowler and Garcia took up the challenge.
When Fowler birdied the 12th, his 7th birdie of the day to that point, he had moved within one of the leader and when McIlroy bogeyed that same hole a few minutes later the pair were tied at 12 under.
McIlroy would dig deep however with birdies at the 14th and an eagle at the 16th and although he bogeyed the 17th his nearest challenger Fowler was struggling with bogeys at the 14th, 16th and 17th.
Fowler birdied the last and at that point was four behind. The final hole is a potential eagle or birdie opportunity but it also has its dangers. McIlroy could all but put a seal of the event if he was able to finish off with a birdie but he did better. A beautiful approach to ten feet set up the eagle chance and when that was holed the margin was six.
"I'm comfortable leading this tournament," said the leader. "This will be the third night I have slept on the lead. It helps that I have been in this position before and have been able to convert and get the job done.
"So I am comfortable with the position I am in but also very comfortable with my golf game. Comfortable with how I am hitting it and really comfortable on the greens.
"I just need to go out there tomorrow and play one more solid round and hopefully that is enough."
Garcia appeared as if he might be McIlroy's nearest challenger when he birdied the 16th to get to 10 under and at that point was within three but a bogey at the 17th and a failure to take advantage of the last could well prove very costly in the final wash-up tomorrow.
After an early birdie had him immediately within two of the lead, three consecutive bogeys before the turn cost Johnson something a whole lot better. He birdied three of his last six holes to give himself an outside chance but it would appear the damage was done with the run of bogeys.
When all was over the best round of the day had come from Daren Clarke whose round of 67 moved him to 12th.
Adam Scott leads the Australians but his chance of contending appears all but gone. He staged a brilliant late recovery from a slow start to get to 6 under par and a share of 7th. Five birdies in his last eight holes have kept to door open for a another fine Open Championship but his winning chances appear forlorn. It would seem he will need a round in the low 60's to have any chance and then rely on McIlroy going backwards. Both seem improbable but not totally out of the question.
Marc Leishman is having by far his best Open Championship and is one behind Scott and in a share of 12th.
Matt Jones is at 1 over, while John Senden, Jason Day and Rhein Gibson are at 4 over.