Ronan O’Gara enjoyed plenty of wet and wild rugby nights during his ­playing days with Munster and this sodden contest would have stirred some fond memories. There was more than a hint of old-school Irish dog in the way his La Rochelle side took an early forward grip on a filthy evening and built a sufficiently big lead to insulate them from a ­concerted Bath fightback.

As the opening salvo to the new Champions Cup season it was also a thought-provoking one for ­English onlookers. Bath sit top of the ­Premiership table and were widely seen as powerful contenders in Pool 2. Here was a reminder that gigantic French Top 14 packs take a good deal of knocking over when they have a point to prove.

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Nor did it help Bath when their captain and key tactical kicker Ben Spencer was ruled out with a tight hamstring on the eve of the game. Without their pivotal scrum-half they were nowhere near their best in a one-sided first half before ­belatedly ­bursting into life in the second. An opportunist try for the lock Quinn Roux did haul the hosts back to within a point late in the third quarter but a subsequent penalty from Ihaia West helped to cement victory for the champions of this tournament in 2022 and 2023.

O’Gara offered a wry ­apology ­afterwards for some audible ­swearing during the game – “That was a tame night for me!” – but the result was a massive plus for his recently ­inconsistent side. In the wake of a shock defeat to Vannes last ­weekend he suggested his team had been ­lacking “attitude, balls and ­character”, which he described as “the ABC cornerstone of any ­successful outfit”. It hardly needed reiterating that he wanted to see a marked improvement, regardless of the inclement conditions.

A damp night is hardly unknown in the west country but the curtains of rain sheeting across the pitch could have belonged to a dark and stormy horror movie. It was certainly an evening to test the resilience of those cast away in the wide open Dyson stand, with prices ranging from £89 to £59 for the ­privilege of a relentless soaking.

It was also swiftly apparent that Storm Darragh was not the only ­irresistible force heading Bath’s way. Opting to use their strong maul as a battering ram, the visitors had two rumbling tries on the board inside the first 26 minutes, first from their back-row forward Oscar Jégou and then their loosehead prop Reda Wardi, following a prolonged drive that had Bath’s forwards backpedalling the full length of their 22.

Despite La Rochelle’s iffy ­domestic form their confidence was visibly growing, as perfectly illustrated by their third try.

Despite a far from sympathetic delivery from the lineout, their Kiwi scrum-half Tawera Kerr-Barlow plucked the ball off his toes as if he was fielding in the gully on a warm summer’s afternoon and darted past the flat-footed cover for a brilliant individual score.

With West kicking all three conversions it put La Rochelle 21-6 up with barely half an hour gone, the kind of advantage that good sides rarely squander. Nor did it help Bath’s cause when a prime attacking position just before the interval was squandered by a botched lineout that ended with the visitors receiving a short-arm penalty for a delayed throw.

It was going to require something special to overturn the 15-point ­deficit with conditions now mostly at the visitors’ backs. And seven minutes after the restart a glimmer of hope duly materialised when a concerted Bath drive yielded a burrowing try for Tom Dunn and Finn Russell curled over a lovely conversion to add to his two first-half penalties.

The game then took a dramatic lurch when Kerr-Barlow, looking to retrieve a kick ahead from the ­excellent Guy Pepper, did not clearly ground the ball in goal and Roux was judged to have touched it down first instead. The evidence was not wholly conclusive either way but Russell’s conversion suddenly made it a one-point ball game nevertheless. Could they somehow complete a ­stunning comeback? West’s 58th-minute penalty made the task harder and, despite a nervous moment or two, it was La Rochelle’s big beasts who had the final say.