1. Diamond could have been a professional star in his own right
The Belvoir Park golfer won the 2012 West of Ireland Championship to earn himself a spot in that year's Irish Open, even if he did miss the cut after shooting rounds of 77 and 74 at Royal Portrush's Dunluce Course.
Diamond also reached the final of the 2011 North of Ireland Championship on the same track and took Patrick McCrudden to a tie-hole round his own course. That's just in case you thought his West win was a one-off. His north coast performance earned him a senior debut for Ireland, who he had also represented at Boys and Youth levels.
In 2014, his handicap was +2.5. In short, he's fairly handy.
2. It's not the first time he has caddied for McIlroy
Diamond was on bag duty during a practice round at the 2005 Irish Open, when the then 16 year-old McIlroy was invited to play in the tournament for the first time. He was again called up for the Par Three tournament at the 2011 Masters and also for the 2014 Alfred Dunhill Links Championship.
3. Diamond and McIlroy are childhood friends
The pair both grew up in Holywood and have long been close friends. Diamond was even on best man duty for Rory's wedding to Erica Stoll last year. Certainly, there are few men McIlroy would feel more comfortable having around the course this weekend than his long-time friend.
4. He's not just a talented golfer
Harry Diamond owns a string of bars and it was his business activities that played a part in his decision not to follow McIlroy into the world of professional golf. His performances at the North and West of Ireland certainly proved his credentials on the course.
5. Could this be a majorly good combination?
Ok so this is a question rather than another thing we know. Diamond has no doubt been a key cog in Rory's rise back to prominence with his first PGA Tour win since 2016 at the Arnold Palmer Invitational in March. Diamond was also on the bag throughout McIlroy's stunning 2019 season, as he won the FedEx Cup after victory at the Tour Championship. The East Lake success was McIlroy's third of the season, after winning The Players Championship and the Canadian Open. Can the pair now go one step further and deliver a major?