Image source, Getty ImagesImage caption, Wout van Aert dedicated his win to the family of Michael Goolaerts, who died at Paris-Roubaix eight years ago
Van Aert and Pogacar entered the famous Roubaix Velodrome together after breaking away from other contenders with about 50km of the 260km race remaining, before the Belgian unleashed a stinging attack an exhausted Pogacar could not respond to.
Victory for Slovenian Pogacar, 27, would have completed the set of the five one-day 'Monument' races, adding to his four Tours de France, Giro d'Italia and two road world titles - but he is left still seeking a Paris-Roubaix win.
Van Aert - so often seen as the nearly man in a golden era of stand-out talents - took advantage of early race drama for both Pogacar and three-time winner Mathieu van der Poel, who suffered a puncture.
The race, traditionally known as the 'Hell of the North', on account of its bone-shaking cobbled sectors, saw Belgium's Jasper Styuven finish third, 13 seconds behind - with Dutchman Van der Poel fourth.
"[I'm] super proud - winning this race means everything to me," said Van Aert, 31, afterwards.
"To finish it off in this way over Pogacar in that world champion's jersey, there's no better way to do it - it's definitely a dream come true.
"I knew on the road with Tadej I had a fair chance once it was just the two of us, and when I truly believed was after Carrefour d'Arbre [a cobbled section]."
Van Aert went on to dedicate his win to the family of Michael Goolaerts, a fellow Belgian rider and team-mate who died during Paris-Roubaix in 2018 when the 23-year-old suffered a cardiac arrest, adding "during recon I got goosebumps – I like to believe he gave me some power [to win today]".
Paris-Roubaix: cycling'’s 'hell of the north'
Sunday was an unseasonably warm spring day in northern France and it meant dust was kicked up into riders' faces on the cobbled sectors, with some competitors struggling to breathe.
Pogacar had to change his bike three times - on the first occasion he was forced to use an unfamiliar 'neutral' service bike on a tight section of pave.
Once he had stopped to collect his preferred replacement bike from his team, Pogacar gave an uncharacteristic bark at a TV camera-bike filming directly on his line of attack, showing signs of stress early on.
As the dust was kicked up on the cobbled sectors, Van der Poel's race was ruined on the infamous Trouee d'Arenberg, still muddy under the trees from the previous day's rain.
Van der Poel punctured and attempted to take a team-mate's bike, but gave up and threw it next to the track before having to wait for a replacement - eventually losing two minutes.
The Dutchman had won the three previous editions of this race - and a fourth straight success would have made him the joint most successful Roubaix champion, alongside Belgians Roger de Vvlaeminck and Tom Boonen.
Upon Van Aert and Pogacar's entrance to the famous velodrome, which sees the race ended over one-and-a-half laps, the crowd roared at the sight of Van Aert, followed by a chorus of boos when Pogacar was announced over the PA system.
"I'm happy for Wout, he deserves the victory," said Pogacar, who typically pulls away from his rivals with several kilometres left in explosive style.
"He never gives up and he is a hero to many young kids, how he rides.
"Every time I tried [to pull away from Wout], my legs were not the greatest any more and [he was always] riding on my wheel."
Wout van Aert (Bel/Visma-Lease a Bike) 5 hours 16 minutes 52 seconds
Mathieu van der Poel (Ned/Alpecin-Premier Tech) +00:15
Christophe Laporte (Fra/Visma-Lease a Bike) +00:15
Tim van Dijke (Ned/Red Bull-Bora-Hansgrohe) +00:15
