Paul Wellens claimed his 24th try of a remarkable season as Challenge Cup winners St Helens marched two points clear at the engage Super League summit.

Wellens, the reigning Man of Steel who looks a decent bet to retain the prestigious award, crossed the line in the second half to put paid to the challenge of a doughty Harlequins outfit.

The Great Britain full-back was on the scoresheet in last week's 30-8 Cup final win against Catalans at Wembley, and his typically predatory score in the 53rd minute against Quins edged Saints 18-10 ahead.

From there they never looked back and Chris Flannery and Lee Gilmour claimed St Helens' fourth and fifth tries to add to first-half scores from Jason Cayless and James Graham.

The visitors, whose play-off ambitions are receding by the week after this sixth game without victory, asked some testing questions of Daniel Anderson's men in the opening period.

Quins wing Ricki Sheriffe scored two first-half tries - his second a brilliant individual effort - as Saints struggled to find their customary rhythm after their Wembley success.

Indeed, Saints were below par for long periods on a filthy night which looked full of omens.

Brian McDermott's men claimed a memorable 14-6 victory against St Helens at Knowsley Road in the second round of the season back in February.

That the win came in atrocious conditions - freezing temperatures ensured the game was played on a snow-covered pitch - which served to expose Saints' difficulties to coping with the elements.

And when Friday night's game kicked off amid driving rain, Saints supporters must have feared the worst.

Cayless' opening try looked to have allayed those worries in the fourth minute.

The New Zealand international prop collected possession, shrugged off a couple of pitiful attempted tackles from Quins players, and crossed the line just wide of the right-hand post.

Teenager Stephen Tyrer added the extras to put Saints 6-0 ahead, but the visitors responded admirably and fashioned a try of their own in the eighth minute.

A well-crafted move down the left flank saw wing Jon Wells halted in his tracks by Wellens, but Quins switched play to the opposite wing with a terrific kick from Danny Orr.

Sheriffe collected and grounded in the corner before producing a delightful effort to claim his second try in 21st minute.

Tyrer failed to control the ball with his feet, allowing Sheriffe to pick up possession and show blistering pace to race 70 metres and cross the line for an exhilarating score.

Henry Paul landed Quins' first conversion from his second attempt but Graham barged over shortly after the half hour mark and Tyrer atoned for earlier error by adding the extras to send his side in at the break 12-10 ahead.

The second half began in dreadfully scrappy fashion, but in the 53rd minute Saints were celebrating as Graham's neat handling sent Wellens scuttling over the line from close range.

Tyrer added a penalty to extend Saints' lead and after Quins lost Scott Hill to the sinbin, Flannery raced clear for the hosts' fourth try.

Harlequins centre Tyrone Smith soon joined Hill in the sinbin and Saints duly took advantage when second row Lee Gilmour barged over the line.

Tyrer maintained his 100 per cent record with the boot with his sixth goal from as many attempts to seal an ultimately emphatic victory.