Danny Care scored the only try as Leinster’s Pool 2 opponents Harlequins, coached by Conor O’Shea, launched the inaugural Champions Cup with a 25-9 victory over Castres.
Care touched down seven days after withdrawing from the Quins team defeated by Leicester in order to be at the side of partner as she gave birth to their first child.
The England scrum-half toasted the highlight of otherwise thrilless night at Twickenham Stoop by rocking his arms in the motion of a baby's cradle.
Care may have finished the try, but it was created by the vision of Nick Evans who found the opening in a previously watertight Castres defence with a crafty double chip.
Evans converted the try and also landed six penalties in a flawless evening that saw him pass 400 points scored in European competition.
Leinster travel to Castres next Sunday in their round two game.
Quins have endured a difficult start to the season, but O'Shea detected the shoots of revival against Castres.
"We haven't been buzzing recently, but it won't take much to get the team buzzing again," O'Shea said.
"That was control, we were really ambitious with the way we played in that first half.
"That was not a weak Castres front five, but our scrum and line-out were excellent.
"We have a long way to go, we know that, but this was a real step forward."
"We have a long way to go, we know that, but this was a real step forward" - Conor O'Shea
O'Shea was delighted Quins had opened their European campaign with a victory not as emphatic as the scoreline suggested and paid tribute to captain Joe Marler.
"Joe is an outstanding scrummager and an outstanding leader who I feel has been unfairly questioned," said O'Shea, who confirmed that Marler left the pitch with a stinger injury.
"That's the world we live in now - people like to comment for the sake of commenting without knowing what's happening behind the scenes.
"I know where he is as a 24-year-old with over 100 games for this club. He has the respect of everyone."