World Cup winner Mike Catt, showing the class England have been lacking, led London Irish to a much-needed victory as they punished Northampton for their mistakes.

Starting the Guinness Premiership match next to bottom of the table, Irish moved into mid-table with a convincing bonus-point win.

Delon Armitage, Justin Bishop, Paul Hodgson, Catt, who also dropped a goal, and Topsy Ojo scored the Irish tries with 20-year-old stand-in fly-half Shane Geraghty contributing 12 points, with three conversions and two penalties.

Northampton replied with a lone try from scrum-half Mark Robinson as they finally found a way through the strong Irish defence.

Irish never looked back after taking the lead with a second-minute try.

It was created by 35-year-old Catt, overlooked for the autumn internationals after playing for England in Australia last summer.

His perfectly-placed kick from the halfway line, found Bishop on the right touchline and he returned the ball inside for Armitage to run in unchallenged.

Northampton were punished for a calamitous series of errors six minutes later.

Hooker Dylan Hartley squandered possession by throwing the ball beyond the line-out, Northampton were then penalised for offside and scrum-half Hodgson took the quick tap penalty to worm his way in between the posts.

Worse was to follow for the Saints. A 15-minute spell of intense pressure, which had Irish defending desperately, counted for nothing when Scottish international prop Tom Smith threw out a bad pass on halfway, allowing Armitage and Bishop to both hack the ball downfield in an untidy chase which ended with Bishop touching down.

Northampton's indiscipline saw Hartley sent to the sin-bin in the 34th minute for a late challenge after Hodgson had kicked to touch and winger Mathieu Bouret was fortunate not to follow him a minute later for a soccer-style sliding tackle trip on Sailosi Tagicakibau.

Catt increased the Irish lead to 25-0 with a confidently laidback long-range drop goal six minutes after halftime and then scored the fourth try to secure the bonus point.

Once more Northampton paid the price for their sloppiness as the veteran kicked ahead and won the chase to touch down after the Saints again spilled the ball in the middle of the field.

Northampton responded with a lone try from Robinson in the left-hand corner.

But Irish tore them apart again for their fifth try, again inspired by Catt. His long pass stretched the visiting defence for Dominic Feaunati to send Ojo over in the right-hand corner.

The defeat leaves Northampton second from bottom and they are now only seven points above basement club Worcester who gained their first win of the season today.

If they cannot improve on this hapless display they will be looking long and hard over their shoulders.