The home side scored the only try of the game through England wing Matt Banahan, but six penalties from the Irish outside half were enough to guide Leinster to a win that put them three points clear of Glasgow Warriors at the top of the table.

A win over Bath at the Aviva Stadium, Dublin, next weekend, where more than 40,000 tickets have already been sold, will end the English club’s hopes of making the last eight and set Leinster on the way to a seventh successive quarter-final.

Leinster bombed a few early chances and then found themselves playing second fiddle for much of the first-half as Bath produced some of their best rugby of the season. Two penalties from Olly Barkley gave the home side a 6-0 lead and it wasn’t until the last minute of the half, and after an earlier miss, Jonny Sexton cut the gap to three points.

Sexton then levelled the scores shortly after the re-start and eventually kicked the champions into the lead after 54 minutes with his third penalty and doubled the lead with a fourth goal on the hour.

But between those two successes Leinster could and should have scored at least one try. A wonderful piece of chasing and regathering by Isa Nacewa put Leinster on the charge in the home 22, but Sean O’Brien ignored the three men unmarked outside him and put his head down in search of the try.

The Irish flanker, last season’s European Player of the Year, was caught and then saw insult added to injury when bath turned over the ball and cleared their lines. There was another close shave for the home defence when Nacewa produced another piece of individual brilliance on the right wing to race past three defenders.

Gordon D’Arcy, Fergus McFadden, Isaac Boss, Jamie Heaslip and then Mike Ross were all held a metre short, but the penalty eventually came and Sexton had no problems from in front of the posts to make it 12-6.

But Bath rallied and two pieces of great skill from their South African back row man Francois Louw, firstly in stealing the ball at a ruck and then making the final pass in the back line to free Jack Cuthbert, helped set up a try for Banahan with 15 minutes left to go.

That left Barkley with the chance to regain the lead with his wide angled conversion and he didn’t make any mistake as he sent his kick straight down the middle to make it 13-12.

Louw then went from hero to zero as he dived over the top of a ruck five metres out from his line to concede a penalty that Sexton easily goaled and a few moments later the Springbok picked up a yellow card.

All that was left was for Leisnter to put a stranglehold on proceedings up front and for Sexton to end the game by bisecting the posts for a sixth time with his latest penalty that helped him to pick up the man of the match award.