Without a win since landing the Convivial Maiden at York in August 2015 for former trainer Luca Cumani, the four-year-old completed an across-the-card Listed race double for the Cheltenham Gold Cup-winning handler following the earlier success of Brick By Brick at Fairyhouse.
Having finished second in a Group Two at the Curragh on her previous start, the 9-4 favourite made the most of her drop in class as she powered two and a half lengths clear of Vintage Folly, completing a double on the day for winning rider Colm O'Donoghue.
Harrington, speaking from Fairyhouse, said: "I was absolutely delighted with her. I sent her over there to get black type because she'd been second in the Group Two last time.
"She did it very easily. It's very important as she's got big black type now. She's been second in a Group Two and been placed in a Listed race as a three-year-old last year.
"She's really come into herself this autumn and she stays in training next year.
"I don't know where she goes next but she may go abroad again."
It did not take long for Classic-winning jockey O'Donoghue to become acquainted with the winner's enclosure at the Norfolk circuit as he steered the Charlie Appleby-trained Imperial Past to victory in the opening division of the Hobgoblin Legendary Ruby Ale/EBF Maiden Stakes.
O'Donoghue said of the 5-2 winner: "He broke smart and travelled good. When I asked for him two and a half furlongs down, he really quickened well.
"He hit the line strong. He is a big horse with plenty of scope."
French Derby hero Intello enjoyed his first winner as a sire in Britain after Regal Reality (9-4) initiated a brace for Sir Michael Stoute and Ryan Moore when making all to take division two of the seven-furlong maiden.
John Marsh, assistant racing manager for owners Cheveley Park Stud, said: "He should improve on that. Sir Michael Stoute likes to creep away with them. Next year is his year, not this year."
Royal winners are always well received and the Stoute-trained and Moore-ridden Swiftsure (2-1) carried the colours of the Queen to success in the Parklands Leisure Holiday Distributors Handicap.
Roger Varian and Andrea Atzeni also teamed up to complete doubles following the victories of Zabeel Prince (8-13) in the Sea-Deer Handicap, and Equitation (3-1) in the concluding Parkdean Resorts Creating Amazing Memories Handicap.
PERFORMANCE OF THE DAY
It may have been a drop down in class for Beautiful Morning in the John Musker, but it was hard not to be impressed with the manner of her victory. She looks more than capable of claiming a Group-race success in the near future.
RIDE OF THE DAY
Ryan Moore is often seen at his best when the going gets tough and had it not been for his persistence in the saddle it could have been a third successive defeat for Swiftsure in the mile-and-a-quarter handicap, which eventually went his way.
TWEET OF THE DAY
Broadcaster Mike Vince was one of the many to congratulate Jessica Harrington on her Listed double achieved both sides of the Irish Sea.
Mike Vince @halo_straight
Wow. Some International double for @Jessica_Racing -
Yarmouth feature and Fairyhouse feature. Great day.