Fullback Tommy Bell scored 24 points as London Irish marked their return to the Premiership in style with a 39-29 victory over Harlequins at Twickenham.
Topsy Ojo and Bell crossed for first-half tries, with Irish's fullback punishing every Quins indiscretion with the boot.
In addition to his try, Bell knocked over two conversions and five penalties, but there was a nervy finish as Joe Marchant, Marland Yarde, Danny Care and Charlie Walker all crossed for Harlequins.
But Brendan McKibbin's bonus-point try gave Irish a winning return to life in the top flight.
Irish had the perfect start as Bell kicked two early penalties before Harlequins' Marcus Smith reduced the deficit.
And Ojo, Irish's all-time leading try-scorer, then produced a stunning break down the left wing to extend his side's lead, despite Quins' continued pressure.
Jamie Roberts knocked on and a quick counter-attack, which saw Ojo play a clever one-two with Fergus Mulchrone, saw the winger touch down.
Bell converted to give Irish a 13-3 lead and the full-back went one better soon after as he took an excellent off-load from Blair Cowan before sprinting clear to extend the advantage.
Harlequins hit back, though, with Roberts feeding Marchant in the midfield, with the outside centre bursting away and under the posts.
Claims of a forward pass by the Wales international were waved away by referee Tom Foley and Smith drop-kicked the ball over the posts quickly to prevent a TMO referral.
Bell's third successful penalty made it 21-10 at half-time.
After the break, with Irish kicking a penalty into the Quins 22, Foley wasted no time in showing replacement Demetri Catrakilis a yellow card for an infringement at the ruck.
Bell knocked over the simple penalty to extend Irish's lead before number eight Ofisa Treviranus completed a fine Irish move on the hour mark for his fifth Premiership try.
But Yarde's dart down the blind side gave Harlequins' hope with 15 minutes left on the clock and, after setting up the winger, Care went over himself to make it 29-22 with six minutes left.
Mike Brown was then shown a yellow card for a block, but it did not stop the fightback as Walker's try reduced the deficit to just three points.
But McKibbin sent the Irish fans into delirium with the bonus-point score which sealed the victory.