Thomas Young made a two-try return for Cardiff Rugby in front of a 12,000 sell-out at the Arms Park, but it was Harlequins who came out on top in this Investec Champions Cup clash.
Back after two months out with a calf injury, flanker Young crossed twice in the first half as the hosts built a 15-7 lead in thrilling fashion.
But ‘Quins fought back in style as they racked up four tries of their own in the opening 40 minutes to turn around with a 28-15 interval advantage.
They went further ahead soon after the break and pulled away in the final quarter with former Cardiff prop Dillon Lewis getting in on the act as he dabbed down after coming on as a replacement.
It was also a happy return to the Arms Park for ‘Quins head coach Danny Wilson who spent three years at the helm in the Welsh capital from 2015 to 2018.
The visitors from south west London thoroughly deserved their win, producing some really incisive attacking as they racked up eight tries in all through a mixture of pace and power, with veteran scrum-half Danny Care named Player of the Match.
But Cardiff also contributed to an entertaining contest, especially in the first half. They now head to Paris for their final Champions Cup pool match against Racing 92 next Saturday.
When the game got underway in front of a capacity crowd, there was to be a dream start for Matt Sherratt’s team.
They took an early lead through a Tinus de Beer penalty and then went further ahead with a try on seven minutes.
Changing direction, South African fly-half De Beer put in a cross kick towards the right touchline where the ball deflected off leaping ‘Quins wing Cameron Anderson and was pocketed by lock Seb Davies who showed quick hands to feed Thomas Young on his inside.
It was then all about the pace of flanker Young as he put the pedal down to run in from 30 metres to the delight of the home fans.
However, it took the visitors just a couple of minutes to respond as hooker Jack Walker rounded off a lineout maul drive that just kept on motoring towards the whitewash, with Marcus Smith converting from wide out.
Midway through the half, Cardiff were forced into a change as Wales squad contender Cam Winnett had to leave the field with a facial injury, which saw Ben Thomas come on at full-back.
Then, on 22 minutes, came Young’s second try and what a score it was. From a ruck in midfield, the hosts moved the ball right through Tomos Williams, Rhys Carre, De Beer, Ben Thomas and Young until it reached Harri Millard.
Winger Millard then sped down the touchline before throwing a pass inside. The ball went to ground, but Tomos Williams was on hand to pick it up and give a no-look return out of the side-door to Millard who popped the scoring pass up to Young.
The flick from scrum-half Williams was a thing of absolute beauty and deserved a try as the end product, with De Beer adding further gloss by slotting the conversion from wide out.
That put Cardiff eight points up and things were looking good, but then we started to see the potent threat of Premiership high flyers Harlequins.
It was all about quick ruck ball and quick hands as centre Andre Esterhuizen crossed out on the left, with flanker Will Evans going over after further concerted pressure to give the visitors the lead.
Then, two minutes from the break, came a key moment. It looked as though Mason Grady had saved a try with a superb tackle as he turned Oscar Beard on his back.
But, after a lengthy TMO review, Irish referee Frank Murphy decided centre Beard had just managed to get the ball down and Smith once again converted from the touchline to put his team 13 points up at the interval.
Cardiff made a change for the start of the second half with Efan Daniel coming on at hooker for Liam Belcher, who had received treatment on a couple of occasions.
The visitors claimed their fifth try five minutes after the resumption when impressive fly-half Smith was worked over in the corner after the ball had been swept left.
Then in the closing stages, they added three further touchdowns from props Lewis and Fin Baxter, plus full-back Tyrone Green, much to the pleasure of the sizeable contingent of traveling fans.