They were just like any other young couple in love, popping in to each other's workplace to give their support on a big day. Except that when Caroline Wozniacki congratulated her boyfriend at the weekend he had just secured a five-birdie finish and victory at the DP World Tour Championship.
"Wozzilroy" – that's McIlroy's own sugary name for them – are one of sport's newest and possibly wealthiest power couples. McIlroy earned more than £3.5m (€4.3m) from golf last year while his assorted sponsorship deals with companies like Jumeirah and Santander are estimated to be worth about £6m a year.
Meanwhile Wozniacki is the second highest-paid female athlete in the world with an estimated income last year from winnings and endorsements of almost £8m.
The couple met last year at David Haye's world heavyweight fight against Wladimir Klitschko. McIlroy had broken up with Holly Sweeney, his childhood sweetheart and a non- celebrity. "Fantastic fight!" Wozniacki gushed on Twitter. "Also met Rory McIlroy, who was sitting just behind me. Really down to earth great guy." The media declared it the perfect love match.
But life for a celeb couple can be cruel. Celebrities set out to court attention and so entire relationships are played out in public. Fame is not liberating, in fact it can be incredibly imprisoning. Public expectation and the fact that nobody is ever far from a mobile phone camera has robbed the famous of any privacy.
The private realm, in which intimacy could flourish, all but disappeared and with it probably the chances of a couple having a real relationship at all. As you become more famous, the list of image makers and corporations that own your behaviour grows. This makes normal, natural behaviour an impossibility, which in turn can only create tensions in a relationship.
This is reflected in a recent survey by the UK's Marriage Foundation on celebrity versus non-celebrity couples that found the divorce rate among celebrity couples who had been married for 10 years was 40pc. The UK national average after the same period was 20. The differences were even greater for shorter periods. One in 10 celebrity couples were divorced after only two years, compared with one in 100 for other couples. A total 25pc of celebrity marriages ended after five years, compared with 7pc for the rest of the population.
In interviews we read that the hardest part of fame was not being able to meet some bright young thing "who's going to love me for me". This is a constant lament from the famous – the way they tell it, they'd love to settle down with a waitress or a shop assistant, but they have to make do with romancing each other because they simply can't find that special "normal person" who isn't overwhelmed by their celebrity.
There are exceptions: Reese Witherspoon and talent agent Jim Toth, Matt Damon and bartender Luciana Barroso, Julia Roberts and camera man Danny Moder. But for the most part, celebrities cling to each other. Their unions are inevitable. This is why we are so obsessed with Angelina Jolie and Brad Pitt. Had they not met on the set of Mr & Mrs Smith, we would have had to set them up.
It must be hard to meet people when you're surrounded by paparazzi. It's also hard to know whether people are interested in being with you for the right reasons and not just for the fame and attention. Celebrities date other celebrities because you don't have to explain yourself or worry about their motivations. They don't idolise you and you don't idolise them back. You've got comfort because you understand each other. They are less likely to kiss and tell.
Lots of celebrities do have flings with ordinary people. What they don't generally do is have long-term relationships with them. Why bother when you can save the serious lovey-dovey stuff for people who really understand you – like, say, other celebrities. Just like with Rory and Caroline who have undoubtedly found that their relationship inevitably means the lenses point ever more intrusively but they are both in it together.