His debut came against Italy in February and he now finds himself at his first Rugby World Cup and at the front of the queue for a starting spot against Ireland in Yokohama, this Sunday after only six caps. It’s all a far cry from four years ago.

He was just 22 when he flew from Brisbane to the UK to begin his new life as a Glasgow Warriors player. When Scotland and Australia met in their quarter-final in 2015, Johnson was sitting alone in his flat in Earl Street, Scotstoun, taking it all in on TV.

He has never attempted to hide his background or his feelings, describing himself as a ‘proud Aussie’ last year and admitting that there were no split loyalties when his native and adopted countries met in what turned out to be a controversial game in Twickenham.

“I am a different person to the one I was four years ago,” he explained yesterday in Tokyo.

“I was just this kid who had come from Australia so I was cheering for Australia. I did not know any better. I had no idea what was going on. I am a completely person now.”

And a completely different player. He was, by his own admission, an overweight and lazy player when he arrived in the northern hemisphere, someone whose focus come a weekend was too often split between a good game and a good night out.

Johnson has been a major success in Glasgow and Gregor Townsend wasted little time in stamping his papers when the residency requirements were satisfied. He has been Glasgow’s player of the year and already has three tries in his first six caps.

The first came against Ireland at Murrayfield last spring but the game ended in a 22-13 defeat for the hosts. Bundee Aki and Chris Farrell provided the midfield opposition that day but it remains to be seen if Aki will have the same partner this time or if Garry Ringrose will start instead.

Johnson has no doubt whom he would rather face.

“You have two pretty direct runners coming down the channels. I’d probably prefer... I don’t know if I should be saying this but I would probably prefer a bigger player running a bit more direct, but we will just wait and see what Ireland chooses.”

He speaks respectfully of Ireland. If there is one thing he remembers from that Murrayfield encounter it is the sheer physicality of it, though he is quick to add that there is more to their next opponents than just brute strength.

Ireland rock up at the weekend with the shiny new tag of world number one hanging around their neck but there is clearly less of a mystique to them for Scotland than there would if it were New Zealand or South Africa they were facing and carrying that same distinction.

Twice he made mention of the neutral venue and it’s use a leveller between these teams and there is the added bonus for Townsend’s side in the handful of injury concerns that have disrupted Ireland’s planning for this Pool A opener.

The narrative has it that the forecast wet weather would favour Joe Schmidt’s side but that is to overlook the likely absence of Rob Kearney and the need to replace him at full-back with one of Jordan Larmour or Andrew Conway.

A barrage of high balls in their direction would be no shock.

“Those two are massive threats ball in hand but we will try to exploit them in different avenues. We will be looking at a bit of film this weekend. Even though there are some really good players who are injury doubts, they would be replaced by Conway and Larmour, who just as good.

“Especially with those two, if you give them a bit of time and space they will do a bit of damage,” said the 26-year old.

“We will look at how we want to play the game tactically and eliminate that threat. We will see what happens.”