The Wicklow-born Irishman, whose parents are Dutch, is often the subject of social media arguments about supposed South African roots, but there is no doubt he is as Irish as they come.
Nobody knows quite where the South African legend came from, and whether the Dutch roots of his surname fuelled a social media fire that simply didn’t exist, but there is no doubt the impact he has had on Leinster and Ireland’s game this season.
The fact that he was snubbed for the British & Irish Lions tour last year seems to only have inspired him to greater heights, as Van der Flier nabbed both the Irish Players’ Player of the Year award as well as the prestigious European Player of the Year award this season, even though Leinster were beaten by La Rochelle in an epic final.
Van der Flier has been sensational, and is often at the heart of Leinster performances and his work-rate has been one of the best on the planet, missing just six tackles in the Heineken Champions’ Cup competition and making the joint-most tackles of any player in the tournament.
At the breakdown he is just as much of a menace, modelling his play on Richie McCaw - and targeting being more effective at a breakdown rather than trying to steal every ball in front of him.
And he has succeeded. In Leinster’s success this season he has been the heart and soul of the pack, and for Ireland has stood out in a similar vein and played a massive role in their win over the All Blacks last season and in the Six Nations campaign this year.
But it is the improvement in his game that has everyone talking. And this Friday he stands out as the biggest threat to the Vodacom Bulls team that arrived in Dublin as massive underdogs.
Van der Flier’s coach Leo Cullen has been gushing in his praise of the flanker, and the example he provides for the rest of the side.
“He’s an incredible character and he’s been outstanding all year,” Cullen said.
“Very dedicated in everything that he does. Meticulous in his preparation. He is a great model for our younger guys as well, just the way he goes about his week. His mindset is to always improve.
"He had an ACL injury in the 2018 Six Nations campaign. All the work that he would’ve done off the field, talking to different people that have had ACL injuries.
“Talking to some of the best back-rowers that he could find out there in the world as well and trying to add bits to his game.
“He’s a great individual, Josh, and he’s had a fantastic season. He came up with a lot of big moments. Unfortunately, he didn’t quite get the team prize but it’s a nice honour for him from an individual point of view,” Cullen said after Van der Flier was awarded the European Player of the Year accolade.
Even Irish legend Brian O’Driscoll has been impressed, and believes the improvements that Van der Flier made to his game this year have been mercurial.
"I think it's probably the level of improvement that we've seen from him," the former Ireland captain said on the Irish radio show Off The Ball.
"It's not just been this last year, it probably started 18 months to two years ago but the progression has been significant. You have to remember that around a year ago, people were pining over the loss of Dan Leavy, Will Connors was back in the mix, and there was the possibility of Peter O'Mahony playing at seven.
"Josh was very much in the conversation to start for Ireland, but he wasn't a mainstay. Now, over the course of the last year or so, he's single-handedly made the number seven jersey his own.
"He was told to improve aspects of his game by Andy Farrell, he's obviously getting great coaching at club level by Leo Cullen and Stuart Lancaster day to day."
"Sometimes players are late bloomers, he's probably now at the peak of his powers physically, and it seems he's maximising his potential now.
"All aspects of his game have improved, but most notably, his ball carrying. Josh always ran good angles but seemed a little bit small for the international stage. That doesn't feel like it's the case anymore.
"His go again when he's hit is phenomenal, leg drive is excellent, and his acceleration helps him pick up good lines on support play. He can be a groundhog when he needs to be and gets through a mountain of work from a tackle point of view.
"He's clever in knowing when to leave rucks alone, he knows how he fits into the defensive system, he's just improved across the board."
This week Van der Flier added Leinster’s Players Player of the Year award to the accolades. Only time will tell if his play adds a Vodacom URC title to an outstanding season thus far.