The Ireland back row was captain of the U20 side that competed at the Junior World Cup here back in 2009. It was a singular honour for a Cork Con boy who wasn't all that long out of his Pres uniform, but the tournament itself didn't go according to plan for a side that had finished second in the Six Nations.

Or for him.

It was a decent Ireland crop ten years ago. Very decent. Head coach Allan Clarke had individual class maturing across the paddock. Ian Madigan played at full-back, Dave Kearney and the late Nevin Spence lined out at wing and centre respectively and the half-back pairing was made up of Ian McKinley and a certain Conor Murray.

The pack probably wasn't inclined to be starstruck.

Jack McGrath was the loosehead and fellow Leinster academy members Dominic Ryan, Mark Flanagan as well as Rhys and Ciaran Ruddock all filled out spots with Munster's O'Mahony charged with the responsibility of on-field lieutenant. That's eight future test internationals and one Italian. Three of them would go on to play for the British and Irish Lions.

Ireland were based down south in Fukuoka for a tournament that was used as a trial run for the real thing in 2019. They started off with a 16-9 win against Argentina at the Mizuho Ground but the win came at a price for O'Mahony who was summoned to the capital for a disciplinary hearing that would cost him any chance of facing the Baby Blacks the second day.

“That was the extent of my trip to Tokyo, unfortunately.”

Ireland lost to the Kiwis, going down 17-0 after keeping the game tight and honest well into the second half. O'Mahony returned for a cakewalk against Uruguay, but they would end their campaign with consecutive losses to Wales and Samoa. Ask the skipper what it was like to play over there and one thing pops to mind like a bead of sweat in a sauna.

“I remember the heat over there,” he recalls. “We played Uruguay at lunchtime and it was 42 degrees pitchside or something like that. It was stomach-churningly hot. There were water breaks every 15 minutes. It was tough going. We lost then to Wales and the wheels came off but it was a great experience.”

O'Mahony, like most players you talk to, loves touring. He knows it is an incredible perk to see such distant and exotic shores with people he regards as friends. Even better? He loves Japanese food. Not everyone feels that way about the cuisine, or the total immersion in such a different way of life, and he admits it can be seen as a “difficult” country to tour.

“Look, it's so different over there,” he explained. “There's a lot of concreted buildings, obviously the language barrier is serious. I love Japanese food but some guys struggle with it over there. They have a great way of life. I think their values are incredible.

“They have incredible respect for people, polite, very helpful, incredibly clean place. It was an incredible experience, as I said, and I am expecting the exact same again, particularly with the World Cup. They are well able to put on a show and an event, so I would imagine it's going to be second to none.”

Whether Ireland can put up a show of their own is another thing.

Nerves frayed by the heavy defeat to England in Twickenham, and a traumatic Six Nations campaign, were settled, somewhat, with the back-to-back wins against Wales before the squad flew out for Tokyo. And yet no-one really knows whether the kinks apparent for most of the calendar year have been fully ironed out just yet.

It makes for a curious backdrop, a side ranked number one in the world but one with a strangely strong scent of uncertainty hanging over their form. If there is an upside to that then it must be the lack of any real hullabaloo over the squad's chances of leaving here with the Webb Ellis in tow come early November.

So many technical aspects of the Irish game have been picked apart and parcelled by now that we seem to have forgotten the aftermath of last spring's home loss to England when much of the post-mortem hinged, once again, on the suspicion that Irish teams just don't cope well with the tag of favouritism.

O'Mahony knows this as well as anyone. He has seen this truism play out across the sporting sphere back home and accepts that most people following the side from the comfort of their homes and local pubs will be some way reassured by the fact that their team at this tournament seems to be lurking in the peloton rather than sprinting ahead on a desperate break for the finish.

It gives you an easier angle at times, but at the end of the day, if you are going to win the World Cup, you are going to have to be incredibly good for a consistent period – the eight weeks or whatever it is.

"So no matter what way you look at it, you're going to have to go and beat the best and play the best rugby you have ever played.

“All this stuff about us not liking the favourites tag, if you're getting to the latter stages, someone is going to have to be favourites and you're going to have to go out and win if you're going to win it. It's not something that we will be overly thinking about but we will certainly be setting our own goals and standards and try sticking with them.”