Bath are cut to the quick by O'Brien

Bath 13 Leinster 18

Somewhere in the dark and dismal surroundings of the Recreation Ground – or the Wreckreation Ground, as Bath's many schadenfreude-soaked rivals have been referring to the rickety old venue on the banks of the Avon for as long as anyone can remember – there is a decent side struggling to find its way towards the sunlight. Unfortunately for the West Countrymen, very much a pioneering force in European rugby, they were exposed to a painful truth yesterday: namely, that there is no point emerging for a mere 60 minutes against reigning champions as effective and resourceful as Leinster. It has to be 80 minutes, or nothing.

Sir Ian McGeechan, the world-renowned Lion King who has spent the last few weeks in one of the very rare downturns to have blighted his coaching career, was understandably pleased with his team's performance in front of a capacity crowd. "I'm very proud," he declared after watching Matt Banahan, the England wing, score the only try of a compelling contest – and a damned fine try at that. "Games of this standard always ebb and flow and are always decided by small margins. It was definitely the case here and as far as work-rate and effort is concerned, I can't fault my players.

"We should have scored more points when we had the floor, as we did for long periods. By contrast, they put the pressure on at important times and when they found they couldn't score the tries, they kicked the penalties instead. But that's what develops in times of success. Leinster spent three or four years learning how to win these matches and now they've reached this point, they're very good at it. We're not there yet, but we're a new team and we know these things don't happen overnight."

It was as accurate a summary as the rugby fraternity have come to expect from the good knight, but beneath the rational and reasoned response to a second European defeat in three outings – one that seriously threatens Bath's chances of progressing to the knock-out stage of the tournament – there were signs that he felt just a little aggrieved. Certainly, there was a knowing twinkle in his eye as, in private session, he discussed events at the tackle area, where the brilliant Irish flanker Sean O'Brien got away with blue murder in the first degree so often that he must now be of interest to every criminologist in the land.

Time and again, O'Brien slowed Bath's possession flow to a trickle; time and again, the referee Jerome Garces turned a blind eye; and it was this, more than anything, that restricted Bath to two first-half penalties and a piddly little three-point lead at the break – a poor return indeed on their high-tempo investment. "Leinster have good players in key positions," McGeechan muttered, his face a picture, "and they do what they do very well. Ask anyone in rugby, be it union or league, what they find most difficult to cope with and they'll say the same thing: quick ball. Leinster have huge experience in making sure opposition ball isn't quick."

Not that O'Brien's performance was entirely destructive. The World Cup forward made a clean break at the end of the first half, sweeping aside both Guy Mercer and Nick Abendanon, and forced Bath into a ruck infringement that allowed Jonathan Sexton to send his side into the dressing room only 6-3 to the bad. O'Brien was at it again from the restart, making a horrible mess of Stephen Donald after Abendanon had sent one of his "interesting" kicks high up into the stratosphere and over his own head. Again, Sexton was able to capitalise from the tee.

Four minutes later, the flanker was on the rampage once more after Isa Nacewa latched onto an imaginative cross-kick from Sexton and set sail up the right. This time, though, he botched it by failing to feed a three-on-one overlap outside him. Perhaps O'Brien assumed he would make the line himself, given that the discombobulated Donald was the only man blocking his passage. If he did, he now knows that assumptions can be costly. Donald somehow brought him to earth a couple of metres short, leaving the Irishman to spend the rest of the game working out ways of minimising the embarrassment.

Still, Leinster were as much in the driving seat now as they had been confined to the boot for the majority of the opening half, Sexton adding penalties either side of the hour-mark to open up a six-point lead. Bath looked spent, their best players – Ryan Caldwell, Francois Louw, Simon Taylor – unable to re-establish their grip. Then, out of nothing, Louw pilfered some ball on the deck to lay the foundations for a counter-attack, hauled himself off the floor, scampered towards the right wing and freed Jack Cuthbert with a wondrous pass. Cuthbert duly fed his fellow, equally elongated wing Banahan for the touchdown, and the home side were back in the argument, especially after Olly Barkley added the extras from left field.

There was, then, a hint of injustice about what happened to Louw from there on in. Garces might have been correct in punishing the Springbok forward for pinching the ball from under Eoin Reddan's nose at a defensive ruck, although the man from Cape Town clearly felt the ball was clear of bodies and therefore his to plunder. Profoundly put out by conceding the penalty that had cost his side the lead, Louw tried to make amends amid the frenzy of the closing minutes, was whistled a second time for intervening from an offside position and promptly packed off to the the cooler. Garces was certainly wrong this time, for Louw had done nothing more than flick out a despairing – and entirely ineffective – arm.

Down to 14 men, Bath's bolt was shot: indeed, Sexton had the last word, landing a sixth penalty with a minimum of fuss from precisely the same spot as the fifth one. As McGeechan said, they know a thing or two, these Dubliners.

Bat h -Try: Banahan. Conversion: Barkley. Penalties: Barkley 2. Leinster - Penalties: Sexton 6.

Bath: N Abendanon; J Cuthbert, D Hipkiss (S Vesty 62), O Barkley, M Banahan; S Donald, M Claassens (C Cook 64); D Flatman (N Catt 73), C Biller, D Wilson (A Perenise 73) , D Attwood, R Caldwell, F Louw (capt), G Mercer, S Taylor.

Leinster: R Kearney; I Nacewa, F McFadden, G D'Arcy (E O'Malley 69), L Fitzgerald: J Sexton, I Boss (E Reddan 62); H Van der Merwe (C Healy h-t), R Strauss (S Cronin 62), M Ross (N White 62), L Cullen (capt), D Browne (D Toner 51), K Mclaughlin (S Jennings 51), S O'Brien, J Heaslip.

Referee: J Garces (France).