Reigning Super League Man of Steel Jamie Lyon grabbed a 24-minute hat-trick of tries as title favourites St Helens put rivals Leeds to the sword in a one-sided clash at Knowsley Road.

Saints, with the Challenge Cup already collecting dust in the trophy cabinet, made mathematically sure of top spot and, on this evidence, will surely complete the double with Grand Final victory at Old Trafford next month.

Leeds hardly knew what hit them as 10-try St Helens struck a rich vein of form from the start, with Lyon claiming a personal haul of 24 points.

Leeds went into the game with an outside chance of claiming the runners-up spot but they were never in the hunt after conceding three tries in the first 10 minutes and a third defeat of the season by St Helens condemned them to a third-place finish.

Lyon, Super League's leading scorer who will return to Australia at the end of the season, got the scoreboard ticking over after only three minutes when he took Keiron Cunningham's deft pass to slip through a gap in the Rhinos defence.

That followed a handling error by Leeds centre Clinton Toopi and another defensive howler from full-back Jordan Tansey three minutes later enabled Jon Wilkin and Lyon to get scrum-half Sean Long over.

While Leeds were all fingers and thumbs, St Helens were at their sublime best, combining awesome strength and stunning handling to run in tries from all over the pitch.

Left winger Francis Meli went in from 80 metres after full-back Paul Wellens collected a wayward Tansey kick and a typically slick passing move enabled Lyon to claim his second try on 20 minutes.

Wilkin, making a surprise return just a fortnight after suffering a badly-broken nose in the Cup final, demonstrated his array of skills by placing a pin-point kick for Lyon to complete his hat-trick seven minutes later.

Leeds briefly stemmed the tide, with centre Keith Senior working winger Ashley Gibson over at the corner but video referee Steve Presley disallowed the try for a knock-on over the line.

Saints had no such problem scoring tries and right winger Ade Gardner took Lyon's pass to claim his side's sixth touchdown five minutes before the break, which could not come quick enough for the shell-shocked visitors.

It could have been even worse for Leeds, with Lyon succeeding with just three of his six conversion attempts but Saints still left the field at half-time to a standing ovation.

The interval pep talk from Rhinos coach Tony Smith instilled much-needed vigour into the visitors, who helped contribute to an evenly-contested second half.

Substitute hooker Shane Millard knocked on with the line open following a superb break from Senior but Leeds finally got on the scoreboard on 55 minutes when winger Scott Donald pounced on Rob Burrow's grubber kick.

But Saints finished well on top, hitting another purple patch that brought them four further tries in just 10 devastating minutes.

Wingmen Meli and Gardner both claimed their second tries and Wellens touched down twice in rapid succession, the second following a clinical break from Wilkin, who once more defied a blood injury to play a major role in his side's success.

There was a comical touch when Lyon passed on the goalkicking duties to 19-stone prop Paul Anderson, who on his last home League appearance, landed the touchline conversion to a rousing ovation.

It compounded Leeds' humiliation but at least they had the final say when Donald and Toopi went over for consolation tries in the last two minutes and Kevin Sinfield took his goal tally to three.