The 21-year-old graduate led his home town in its annual celebrations on horseback, bike and foot.
Festival chairman Douglas Hardie installed Harry with his sash of office in a poginant ceremony at Melrose Abbey on Thursday night.
And the importance of the occasion was not lost on the young graduate.
Harry said: “Throughout my time growing up in Melrose, I have walked down Coulters Road behind us to watch the crowning ceremony.
“Leaving my house, I was always excited to watch the event. I never failed to observe in slight awe as I took in this great, ancient tradition under the abbey walls.
“To be standing here with the famous yellow and black sash around my chest is a truly amazing and surreal feeling.
“I do assure you I am deeply conscious of the great honour you have bestowed on me and my family.”
“These past few weeks, I have had the privilege to represent the town at Hawick and Selkirk and look forward to doing so at the festivals and common ridings yet to come.”
He described the well wishes and generosity from the Melrose community as “overwhelming” and added: “I hope our 2018 festival will continue to generate many fond and happy memories for us all.”
Last week was an important one too for festival queen Thea Foulkes and her court, who carried out their part of the ceremonies faultlessly on Thursday and Saturday.
On Monday night, more than 200 riders followed Harry on horseback around this year’s new rideout route, before cyclists young and old donned their helmets for Wednesday’s community bike ride and barbecue in Annay Road.
Wet weather on Tuesday night failed to deter townfolk from enjoying a fancy-dress contest while the sun made a welcome reappearance on Friday for the Melrosian’s visit the town’s schools and hospital before that evening’s ball.
Saturday’s tour of ceremonies went without a hitch, with the party receiving a warm welcome at each historic site before the ceremonies concluded with Thea laying a wreath at the burial site of King Robert the Bruce’s heart within the abbey.
An afternoon of sports, music from the pipe band and the festival dinner followed, drawing the festival to a close.
Harry said afterwards: “It was such a busy week but an absolutely amazing one.
“It’s amazing how much you can actually fit into a week from the kirking to the dinner.
“It was great to see so many friends and family there. The rideout was very well attended, and I think a lot of people were quite intrigued by the new route.
“On Thursday evenin,g it was quite surreal being up there myself after being at the installation so many times as a youngster.
“The queen and her court did a great job. They are all a very good group of kids.”
Joining Thea in her court were attendants Grace McWhinnie and Sophie McGarry, courtiers Jamie Whiting and Toby Swan, heralds Brodie Henderson and Mario Gee and train-bearers Emma Wear and Ruby Jackson.
Harry was supported by his parents, sister, grandparents and his visiting wider family.
“Some of them were from London,” he added, “so it’s all quite new to them. They were shocked by just how big the Melrose Festival is.”
Mr Hardie added: “The 2018 Melrose Festival was extremely successful with our outstanding young principals, Melrosian Harry Fletcher and Queen Thea and her court, carrying out their duties superbly well. In addition a special mention for our principal guests Liam and Marnie Harvey who proved to be extremely popular. The festival happens as a result of a lot of hard work and I am indebted to the festival executive for their ongoing time commitment and effort. Thanks also to our patrons, those who participated and all who came along to support.”