Further touchdowns from replacements Tadhg Furlong and Darragh Fanning helped Leinster maintain momentum upon the resumption and, after the French side responded with a 70th-minute score from Romain Martial, replacement scrum-half Luke McGrath completed a memorable night for Leinster by registering their seventh try of the game.

Speaking directly after a distinctly one-sided encounter, O’Connor agreed that it was one of the Blues’ best defensive performances of the season.

“Yeah, probably,” he said. “The preparation was very, very good throughout the week.

“We knew that Castres’ motivation would be questionable, so if we got a platform up front there would be space to play, and we tried to tap and go, counter-attack and build phases – that way by making them work really hard, and we got the benefit out of it.”

Given the woes of Castres in the inaugural year of the Champions Cup, O’Connor felt it was necessary for Leinster to keep the ball in play for as long as possible.

Kearney’s second-minute try was still a welcome surprise, however, and he was thrilled to see Cronin crossing for a bonus-point score on the stroke of 40 minutes, which offered them the luxury of resting players ahead of next week’s crunch sixth-round trip to Coventry to face Wasps.

“The plan was to try to fit as much ball in play in the 80 minutes as possible,” O’Connor added.

“We thought that if we could do that, given the conditions, that we would get pay out of it at some point. We didn’t think we’d get pay as early as we did with Dave’s try, but it was a great way to start the game.

“We were a little bit untidy after that, but I thought the composure to keep playing throughout the first half was important. To come away with four tries in the first 40 gave us the luxury to rest guys up and manage the (squad of) 23.”

Castres did not provide a coach or player to talk to the media after the game.