Tom Williams crossed for two tries and fellow wing Ugo Monye, who made his 200th appearance for Quins, crossed for another of the home side's six scores.

Connacht, who announced the appointment of Pat Lam, the former Auckland Blues coach, as the successor to Eric Elwood before kick off, made a first of it in a compelling first half but Quins' ran riot in the second period.

The English aristocrats have been the dominant team in Pool 3 and already had a 10-point lead over their nearest rivals, Biarritz, after Round 4 and they have now secured qualification with a game left to play.

Fly-halves Nick Evans of Harlequins and Connacht's Matthew Jarvis swapped early penalties before the home side were awarded a penalty try after the visitors collapsed a series of scrums in the shadow of their own posts.

Evans slotted over his third penalty to make it 16-3 at half-time, but in the second half Quins proved their status as genuine contenders for the title with a powerful pack performance.

Williams scored Harlequins' second and third tries at start of the second half when Connacht were down to 13 men, with flanker Johnny O'Connor and wing Fetu'u Vainokolo in the sin-bin.

Referee Neil Paterson also yellow carded Harlequins prop Joe Marler and Connacht's replacement hooker Ethienne Reynecke before O'Connor crossed for a consolation try for Connacht.

Replacement centres George Lowe and Ben Botica both crossed for late tries as Harlequins rubbed salt in Connacht's wounds in securing yet another impressive Heineken Cup victory.