Returning to France barely 100 days after their World Cup dreams were crushed in Paris, Ireland strode out at Stade Velodrome to face another bruising test of their mettle.

The Six Nations is a different beast. Marseille is a fair jaunt down the road from Paris, but still Ireland fielded questions all week about World Cup hangovers, navigating the post-Johnny Sexton era and putting things right.

This was always going to be an important result, win or lose.

France were in the same boat. After agony in their home World Cup, they too were wounded and forced to fight on without their captain Antoine Dupont, who is Olympics-bound with the Sevens.

The Six Nations is tough enough, but it becomes even more daunting without the best player in the world.

And so it proved. Just like 12 months ago when Dublin hosted a rip-roaring encounter, there were smiling Irish eyes and sullen French faces on a night when the reigning Grand Slam champions let everyone know that theirs would be a crown not readily surrendered.

In recent years, when these two have gone at it, the rugby world has been invariably treated to unforgettable spectacles of stunning speed, ferocity and drama.

Friday night's curtain-raiser was no different.

For the first half an hour, though, it was all about Ireland.

With the line-out issues that cropped up at the World Cup seemingly resolved and with a Herculean second row unit of Tadhg Beirne and Joe McCarthy leading the way, a largely stress-free night beckoned after Jamison Gibson-Park and Beirne tries were followed by Paul Willemse's dismissal for France just after the half-hour.

Disturbed by an eerily silent crowd, France stirred and Damian Penaud burst into life to score his 36th try in 49 international games. Game on.

At half-time, with the home fans having found their voice, a roaring France assault on the Ireland line in the second half seemed inevitable.

But it wasn't until after Ireland's third try - from one of their fresher faces in Calvin Nash - that the holders really found themselves under the pump, with the double-whammy of Paul Gabrillagues' try and Peter O'Mahony's yellow card inviting furrowed brows from the Ireland coaches.

What happened next was the most pleasing aspect for head coach Andy Farrell.

Instead of caving under France pressure, as several Ireland teams have done down the years, the players embraced the chaos and stuck together while their over-worked hosts finally wilted.

Recently, Ireland have been adept at finding clarity and composure when they need it most. They found it in Dunedin to silence New Zealand, they found it in Paris when they crushed South Africa and they found it in Dublin last year to see the Grand Slam home against England.

They found it here, too, pummelling a wearying France in the closing stages until Conor Murray gleefully booted the ball into the stands to seal what is probably his side's greatest win over France.

"It's something we've continued to work hard on, making sure that we don't get too ahead of ourselves or too down on ourselves," said Farrell, referencing Ireland's response to the Gabrillagues try.

"We were excellent in that regard, albeit [there was] a 10-minute period before half-time when there was a knock-on effect of a couple of penalties we gave away.

"We lost our way a little bit at the start of the second half, but all in all I thought we were really good.

"The players spoke about it after the game - the composure was great and we were able to get on to the next moment. We didn't become too fazed."

One of the key storylines heading into the game was the sense of new beginnings for Ireland, with O'Mahony's captaincy and Jack Crowley taking the number 10 shirt from the retired Sexton chief among them.

Both faced difficult moments here. O'Mahony spent 10 minutes of the second half in the bin, while Crowley was forced to summon the stubborn resolve that set his predecessor apart after missing a first-half penalty from 35 metres.

While his performance was far from pristine, Crowley showed strength of will by continuing to orchestrate Ireland's attack - teeing up Beirne's try with a lovely pass - and nailing two stunning second-half conversions from the sideline.

"He typifies what we're talking about," Farrell said of Crowley, who kicked 13 points.

"His composure at the line was great. He made some really nice decisions and some poor ones as well, and he'll know that better than anyone.

"The strength of character with his goal-kicking. To miss that one in front but then to knock them over from the sideline showed immense character.

"It's a good start for him and for us as a team. Hopefully he'll get better and we'll benefit from that as well."

Ireland don't like to look too far ahead.

The World Cup pain is buried. Now they must get used to being asked about back-to-back Grand Slams.

A record win over your biggest challengers will do that.