Christensen was the only amateur to make it through final qualifying across four venues.
A birdie-birdie finish completed a brilliant fightback by the Northern Irishman.
It was McIlroy’s first win on Scottish soil.
Tony Jacklin was that last Englishman to win an Open title in England back in 1969.
A third round of 67 ensured halfway leader McIlroy remained the man to catch at The Renaissance Club on 13 under par.
The elder Fitzpatrick has a US Open and two Ryder Cup appearances on his CV.
The Briton hit six birdies leaving him tied in second place going into the third day of the tournament.
McIlroy added a second round of 66 to his opening 64 at the Renaissance Club to reach 10 under par.
Harrington has not won on the DP World Tour since 2016 but has claimed five victories on the Champions Tour in the last 13 months.
The Englishman shares the clubhouse lead after starting the day eight shots off top spot.
