Leinster rose to the top of the roll of honour in the Pro 14/ 12/ Magners League/ Celtic League with an entertaining win over Scarlets at the weekend, the first time they've occupied the summit on their own since winning the inaugural tournament in December 2001.

Their first ever European Cup and domestic title double set the seal on a stunning year on the pitch for Irish rugby.

Ireland won the Grand Slam with such ease in the end that supporters had to be reminded that this was only their third ever.

In contrast to the 2009 Grand Slam finale, when heart-rates rose to dangerous levels, Irish fans in Twickenham spent the final quarter of the game in a celebratory, self-satisfied stupor, draped in tricolours and trying to catch their faces on the big screen.

In that context, it was easy to forget how rare an achievement it was for Irish rugby.

As of now, they sit at No. 2 in the world rankings and are on a 12-game winning streak. While past history cautions us against over optimism, Ireland couldn't be better primed for the Japan World Cup in 16 months time.

The champagne flows in the Twickenham dressing room after Ireland claim the Grand Slam

As for Leinster, it's hard to see things can improve from here. That's the only downer. They are in the inverse of the situation that Northern Irish pop outfit D-Ream sang about in the 1990s.

Things can only get worse.

On Against the Head last night, host Daire O'Brien was minded to quote the late darts commentator Sid Waddell speaking about the late darts champion Eric Bristow, comparing him to Alexander the Great.

"When Alexander of Macedonia was 33, he cried salt tears because there were no more worlds to conquer... Bristow's only 27."

Perhaps the most startling detail is the number of Leinster and Ireland players who went through the 2017-18 season without losing a game for club or country.

Johnny Sexton, Rob Kearney, Tadhg Furlong, James Ryan, Garry Ringrose and Robbie Henshaw all went the season without tasting defeat.

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What's curious is that this, the most successful ever season for Irish rugby on the pitch, coincided with a series of things going awry off the pitch.

The upper echelons of the IRFU have been widely praised for far-sighted decisions taken 20 years ago, which apparently laid the grounds for present success - though there are those who debate whether they're actually due much of it.

Stephen Jones of the Sunday Times, a man whom Irish rugby fans have religiously hate-read for the guts of 18 years, thinks they deserve zero credit whatsoever and it was only pure dumb luck that the provinces already existed as organic structures, perfectly adapted for the emerging European club game.

But Irish rugby is yielding the benefit of decisions taken by administrators in years gone by.

In late 2011, for example, panicked by Ireland's relatively poor stock of front rows - a failing which would lead to humiliation in Twickenham in 2012 - the IRFU opted to restrict the number of foreign imports allowable in the provinces.

Six and a half years later, Ireland has props aplenty with Tadhg Furlong one of the leading players in his position in the world.

The panel on the deep roots of Leinster and Irish success - "It's more than a great year... we have a unique system in Ireland which is only replicated in the southern hemisphere" pic.twitter.com/Ji8lLOWvIy — RTÉ Rugby (@RTErugby) May 28, 2018

So, while the IRFU has seen many good days, few of them were this year.

Bizarrely, in spite of all the on-field glory, this was in many respects a traumatic season off the pitch for Irish rugby.

Let's give the rundown.

At the end of last year, we learned that the 2023 World Cup would not be coming here after all, and would instead rugby's premier tournament would be returning to France for the second time in what feels like a fortnight.

For much of the past couple of years, the country had talked itself into thinking itself a shoe-in, largely on the basis that the other had already held the thing and it was our turn.

But no, much to the IRFU's shock and obvious chagrin, the Irish bid was ripped asunder at the technical report stage and duly finished bottom in the voting a couple of weeks later.

Not even our Celtic League compadres saw fit to toss us a vote at the fateful hour.

At the beginning of January, we had the explosion of the Gerbrandt Grobler saga which sparked a week of testy interviews and left a sour taste in many mouths.

Grobler served a two year ban after testing positive for the anabolic steroid drostanolone while playing for Western Province in South Africa.

Opinions were divided being those who believed he should get a second chance and those who felt the Munster brand would be diminished by fielding such a player.

IRFU chief executive Philip Browne argued that Grobler was a young man who'd made a mistake and who, now, happily, was in much healthier and cleaner rugby environment.

Under pressure, he acknowledged that the IRFU might have to develop a process around the hiring of players to avoid such a controversy blowing up again.

Most traumatic of all by some distance was the Belfast trial of Paddy Jackson and Stuart Olding. The pair were found not guilty of rape by the jury in late March.

However, the revelations during the trial, most notably the publication of whatsapp messages - which Jackson later admitted were "degrading and offensive" - saw pressure come on the IRFU and Ulster Rugby to terminate their contracts.

The pair had their contracts revoked on 14 April.

Ulster, who had a nightmarish season all round, admitted to feeling a great deal of sadness over the pair's sacking.

There were other more humdrum and minor annoyances.

A couple centred around Leinster's rather chaotic mini-tour of South Africa for the Pro 14. In an otherwise near flawless year for Leinster rugby, the trip saw a couple of logistics faux pas which would have had Roy Keane on the first flight back to Cheshire.

The problems started once they landed in South African soil. Two of their number, Isa Nacewa and Jamison Gibson-Park were denied entry to the country and they had to turn back and head home.

The pair had no visas because Leinster presumed they wouldn't need them. Both had played Super Rugby in Johannesburg, freely entering the country on New Zealand passports and it was thought these would suffice once more.

Alas, the law had been changed recently and the visa-less players had to fly back to Dublin. They were flown out in time for the game against the Southern Kings but due to the haphazard preparations weren't used until the following week.

Isa Nacewa and Jack Conan take the field before the game against the Cheetahs

That wasn't the end of it.

Cian Healy was involved in a rather strange incident when he asked to disembark the plane when the Leinster team were flying from Port Elizabeth to Cape Town.

Healy refused to heed the call to switch off all electric equipment and persisted in using his laptop on the plane.

A member of cabin crew demanded the plane be turned around and Healy was asked to leave when it returned to the terminal.

He took the next flight out and apologised over the incident.

On the playing front, Irish rugby lost the services of both Simon Zebo and Donnacha Ryan, with the former still shy of his 28th birthday (at the time anyway) and with seemingly plenty left to give.

And then there was the rather messy and high-handed attempt later in the year to bundle either Joey Carbery or Ross Byrne off to the Ulster, despite the reservations of both players.

This last incident showed the complications and the occasional snags of the Irish system, otherwise the envy of the northern hemisphere. Essentially, Ireland's heir apparent at No. 10 is not playing all that much rugby at No. 10.

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The chaotic off-field shenanigans provided a curious background to a season of unprecedented success on the pitch.

The mostly irreproachable Joe Schmidt now takes a squad to Australia for a three-test summer tour, with the possibility of extending their winning run to 15 games.

It is the first time Ireland have toured Australia exclusively since 1999, a tour most famous for giving Brian O'Driscoll his first Ireland cap.

With a Grand Slam won and a historic victory over New Zealand already achieved, the next item to chalk off rugby country's bucket list is ending Ireland's ignoble record of having never gotten by a World Cup quarter-final.

The meticulous Schmidt will have an eye towards Japan in everything he does for the next while.