But Munster lost their composure in the final moments and Racing's midfield pair Barkley and Mirco Bergamasco made them pay a heavy price with two late penalties.

Munster hung on for a losing bonus point but will be frustrated not to have built on their early 10-0 lead.

The conditions in Paris looked to have played into Munster's hands as torrential rain fell throughout the day.

Paul O'Connell was passed fit to play his first game of the season and the old warrior galvanised the Irish pack that dominated the early exchanges.

It was from a series of scrums within sniffing distance of the Racing try line that O'Gara opened the scoring with a penalty that saw him surpass 1,300 points and cap his position as the greatest kicker in this tournament's history.

Moments later and O'Gara added a conversion when flanker Sean Dougall shrugged off two tackles to score under the posts.

Peter Mahony was then held up over the line as Munster went for the jugular only to suffer a double blow before half-time when man of the match Maxime Machenaud pounced on a reckless pass by O'Gara, who subsequently limped off injured.

Barkley added penalties either side of the break before he and his midfield colleague slotted their late winners.