Losing all four of their warm-up games before making hard work of beating USA in their opening Pool C encounter, Ireland were given little chance of upsetting one of the tournament favourites in their second game.

But with Australia’s pack hindered by the late losses of outstanding flanker David Pocock and first-choice hooker Stephen Moore, O’Driscoll’s men seized their chance.

Jonathan Sexton fired over two penalties and a drop goal before the experienced Ronan O’Gara came off the bench to slot six points off his own and finish off the Wallabies, who managed just two James O’Connor penalties.

And after bouncing back from a woeful summer to perform when it mattered most, O’Driscoll insisted there was still work to do.

“It was the performance we knew we had in us,” he said. “We swear we were in Dublin with that crowd. Absolutely incredible support and it was our job to give them something to shout about and thankfully we did.

“It's just half the job done. We have two wins and two more to get so, as much as we'll enjoy this, let's not lose sight there are two more games.”

The margin of victory denied Australia a losing bonus point and was almost increased at the death when Tommy Bowe was dragged down just short of the line after a lung-busting break away from inside his own 22.

Ireland now sit proudly at the top of Pool C and coach Declan Kidney admitted their success had been built on a solid forward effort.

“I was pleased with the way we went about our business,” he said. “We managed to stifle a very good Australian side. I think our scrum is getting a little stronger.

“We still have a little bit of work to do. The work really starts now.”