Ireland were heading into that year's Autumn internationals as Grand Slam champions after Ronan O'Gara's late nerves-of-steel drop-goal in Cardiff that March.

The Munster out-half would start the opening game in the series as Ireland and Australia drew at Lansdowne Road.

The following week, Fiji were the visitors to the RDS as Jonny Sexton made his international debut. RTÉ Sport's report of the match called the Dubliner's performance 'highly-impressive' as he kicked 16 points of the team's total of 41.

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Sexton's 100% record against the Pacific Islanders saw him selected to start against South Africa six days later at Croke Park.

It was the first time that O'Gara had been dropped in six years, and then coach Declan Kidiney explained his thinking behind the decision.

"I need to find out more about Jonathan. I worked with him last year and played him in the A team. Ronan is disappointed but Ronan being Ronan, he's still contributing to the team this week. It doesn't matter that it was a difficult call, my job is to pick the team."

The call was ultimately justified as Sexton kicked all of Ireland's points as they beat the World Champions 15-10.

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Despite his showing in those Autumn internationals, Sexton was once again warming the bench by the time the following year's Six Nations rolled around.

It took France ending Ireland's 12-match unbeaten run for Declan Kidney to decide to change things up as they headed to London to take on the Martin Johnson-coached England.

It was a wet day at Twickenham and Sexton made his Six Nations debut as Ireland ultimately got the show back on the road with a victory. The critical scores came in the last 10 minutes, and by that time O'Gara had been brought on.

Even so, the Leinster number 10 had done enough and he started the final two games of the campaign, including his first Six Nations game in Dublin in the victory over Wales.

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The end of year internationals in 2010, including defeats to South Africa and New Zealand, were followed by an average Six Nations campaign where Ireland beat England, but lost to France and Wales.

Ireland headed to New Zealand for the World Cup off the back of defeats in four of their warm up tests, and they weren't among the favourites for the tournament.

Sexton made his World Cup debut against the USA at the Stadium Taranaki, but his kicking return of two from six that day wasn't would he would have wished for.

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Nevertheless, Sexton started the big one against Australia, as Ireland went on to record their first tournament victory over one of the powerhouses of southern hemisphere rugby.

As if to emphasise the question marks around Sexton's place kicking at that time, O'Gara came on late in the game, replacing the injured Gordon D'Arcy. With the two out-halves on the field, it was the Munster number 10 who took over the kicking duties, landing two crucial penalties.

A colourful discussion amongst the RTÉ Rugby pundits saw Conor O'Shea declare that, "Ronan O'Gara's place kicking in a tight match, at the moment, is superior to Johnny Sexton's."

And Kidney returned to what he knew best as O'Gara would start Ireland's three remaining games at the tournament and Sexton was dropped.

Ireland headed to the quarter-final as the Pool C group winners but Wales, as they had done in that year's Six Nations, out-classed Ireland as Warren Gatland got one over on his former colleague Declan Kidney.

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2012 was a bit of a dud year for Ireland as they managed just two wins in the Six Nations, before losing thrice to New Zealand in their summer tour.

The Autumn internationals were mixed as the team lost to South Africa before going on to beat Argentina in the Autumn internationals.

While Ireland were heading in the wrong direction, for Sexton it was a season that saw him make the number 10 jersey his own, as he started all games that season, bar a non-capped victory over Fiji.

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2013 was a bad year for Ireland as they recorded their worst ever performance since the tournament became the Six Nations.

They managed a single victory, even if it did come against the perennial thorn in the side foes of Wales, but three defeats - and particularly the to date only defeat ever suffered against Italy in the competition - meant that the writing was on the wall for Declan Kidney.

Sexton played the Wales game but didn't make it to half time against England in Dublin as he suffered an injury which ruled him out of the rest of the tournament.

But Kidney was to be replaced by someone very familiar to Sexton as his Leinster coach Joe Schmidt took the job, following back-to-back European Cup wins with the province.

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A heart-breaking defeat to New Zealand the previous Autumn had hinted that, despite the result, Ireland were beginning to head in the right direction in the very early days of the Schmidt reign.

The 2014 Six Nations went well for Ireland as they won three of their first four games to give themselves a shot at the title against France.

Events earlier that day meant Ireland knew any victory at Saint Denis would be enough to claim a first title in five years.

The match ebbed and flowed, and while Sexton didn't have one of his better afternoons from the kicking tee, he went over for two tries as Ireland gave Brian O'Driscoll a fitting send off.

Sexton ended the tournament having scored the most points of any player, and the joint-highest number of tries with four.

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2015 was a World Cup year, and Ireland were looking to do a first unshared back-to-back brace of titles since the 1940s.

Getting over France and England has traditionally been seen as the key to landing any Six Nations, and Ireland had managed that already as they headed to Cardiff for a round four clash with Wales.

Sexton earned his 50th cap but Gatland's charges put paid to hopes of a Grand Slam.

The team had to regroup to face Scotland in the final game in Edinburgh, and results earlier in the day meant that they needed a 21-point winning margin in order to move past the Welsh in the table, with England still to play later in the day.

Ireland did their job as Sexton kicked eight of his 10 kicks on the way to a 30-point winning margin, and with England failing to win by enough in London Schmidt's squad had defended their title.

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After the trek to New Zealand in 2011, England and Cardiff hosted the 2015 edition, allowing for large numbers of supporters to make the short journey across the Irish Sea.

Once again the early part of the tournament went well as Ireland topped Pool D. But ultimately the victory in their final pool stage match against France proved to be a pyrrhic one.

Paul O'Connell, Peter O'Mahony, Jared Payne and the suspended Sean O'Brien were already set to miss the quarter-final against Argentina, when it was confirmed that Sexton, who had been taken off in the first half of the victory over Les Bleus, would be added to that list.

As is Ireland's wont on the game's biggest stage, the last eight would prove to the furthest they would go in the tournament as early tries from Matias Moroni and Juan Imhoff set the south Americans on their way to victory.

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The Six Nations after a World Cup can often be disjointed, and thus it proved for Ireland as they relinquished their grip on the title.

Sexton kicked a late penalty to earn a draw against Wales in Dublin but trips to Paris and London proved beyond the side as they finished third in the table.

The highlight of the year was undoubtedly a first ever victory over New Zealand. Sexton got an hour at Soldiers Field as Jordi Murphy, CJ Stander and Conor Murray gave the start they needed to finally see off the All Blacks.

Victories against South Africa and Australia showed the potential that still existed in the Ireland squad, although Sexton did miss the tour of the Rainbow Nation.

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2017 saw Ireland finish second in the Six Nations table as Sexton missed the opening two games of the championship with a calf injury suffered while playing for Leinster.

He returned to lead the team to victory over France in Dublin in round three. The following day in Cardiff, Ireland were beaten as Sexton came on and off the pitch twice - once after taking a knock and the other for a yellow card - in a 13-point defeat against Wales.

After a second Lions tour that summer, Sexton was back in the Ireland team for two of their three Autumn internationals, as they annihilated South Africa and exacted a modicum of revenge on Argentina in Dublin.

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2018 was a golden year for Ireland as they claimed just their third Grand Slam.

As in 2009 there was an iconic kick for the ages, but this time it came in the first match.

The visitors to the Stade de France went through a full 41 phases before Sexton drop kicked the ball between the sticks with the last play of the match.

Sexton started the next four games as they made it five wins from five and joined the teams of '48 and '09 in claiming the Grand Slam.

Was the Ireland fly-half's drop kick the greatest piece of individual skill you saw in 2018? #RTEsport #RTEsportawards https://t.co/ToMecHb5qZ pic.twitter.com/L4vnv8m3sd

— RTÉ Sport (@RTEsport) December 14, 2018

The glory of the spring was followed up by a tour to Australia in June looking for a first series win in the southern hemisphere since 1979.

Sexton was benched for the first game as Ireland went down by nine points in Brisbane. He returned for tests two and three, kicking 16 and 15 points respectively as Ireland kept their fine year going.

And they finished the year with three wins from three in their Autumn internationals, including a first ever home win over New Zealand in a game where Sexton kicked four from four.

Sexton was rewarded for his consistency throughout the year by becoming only the second Irishman to win the World Rugby Player of the Year award.

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Ireland's chances of retaining their Six Nations crown were already in trouble when they lost the opening game of the tournament to England in Dublin.

They recovered to win the next three but Wales outclassed them in Cardiff on the last day to claim a Grand Slam of their own. Sexton had started all five games.

As the World Cup approached Ireland reached the top of the world rankings for the first, and to date, only time after beating Wales in back-to-back warm-up games in Cardiff and Dublin. Those games had also included a record defeat to England in London.

Sexton was in the team for the World Cup opener as Ireland impressed in getting past Scotland, but the number 10 picked up a thigh injury which would rule him out of the second pool fixture against hosts Japan.

Sexton-less Ireland were beaten by the hosts, which meant facing New Zealand - rather than South Africa - in the last eight. And the All Blacks put Ireland, who had beaten them twice in that World Cup cycle, back in their box with a seven-try, 46-14 victory in Tokyo.

Sexton, back in the team, had a bad day at office, failing to score while missing touch with a number of kicks.

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While some presumed that the 2019 World Cup might be the end of Sexton's international career, he has continued to play a central role.

He once again started all five games in last year's Covid-19 disrupted Six Nations, as Ireland had a chance of taking the title on the last day in Paris.

There were no summer or autumn internationals because of the pandemic, but Sexton was once again the number one out-half for Ireland in this year's Six Nations.

He kicked a late winner in Edinburgh as Ireland nearly threw away victory, while he kicked eight from eight as Ireland finished the tournament on a high, beating England in Dublin. He missed the defeat to France at the Aviva after failing to recover from a head knock suffered in the defeat to Wales in the opening week.

He hinted earlier this year that the next World Cup might be beyond him, saying that, "If we talk about World Cup cycles, I might not be part of the full cycle..."

Despite missing out on the Lions Tour, he was rested for the summer meetings with Japan and the USA, but he has been named for this weekend's Autumn international against the Cherry Blossoms, and who is to say what number of caps he might reach in the end.

New Zealand and Argentina are also due to visit Dublin before the end of the month.

Jonathan Sexton admits he "never in a million years" thought he would make it to Ireland 100 caps, which the 36-year-old will do against Japan on Saturday, 12 years after making his debut. #IREvJPN pic.twitter.com/MMibFAJOYx

— RTÉ Rugby (@RTErugby) November 2, 2021

Follow Ireland's November internationals v Japan, New Zealand and Argentina via our live blogs on RTÉ.ie/sport or the RTÉ News app, or watch live on RTÉ2 and RTÉ Player. Live commentary on RTÉ Radio 1.