His quality had long been recognised among regular attenders at Scotstoun, but his celebrity did not extend much beyond that until he spotted a glimmer of an opening, seized it and stepped into the limelight, before sidestepping his way across the opposition line.

If, at point blank range, the centre had somehow been able to defy the odds by producing a tackle that George Ford from scoring a few minutes later, Scotland’s meeting with England at Twickenham 12 days ago would be forever remembered as Sam Johnson’s game. As it was it has ensured that he will attract a good deal more attention off the field as well as on it in the years to come as he began to realise almost immediately.

“I haven't watched the game back (but) obviously, I've seen my try a couple of times,” he said.

“I'm not really big on social media but my girlfriend showed me a few reactions from people watching at home. The biggest buzz I got out of all of it was seeing how happy it made people around the country.

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“That's something you don't really realise when you're doing it. To see that kind of reaction is such a good feeling.”

Coming to terms with it all took a bit of time.

“That was my first taste of international rugby. The Six Nations is as emotionally hard as it is physically,” said Johnson.

“For me personally, my body didn't want to move until the Wednesday after that weekend, but it's all good now and I'm ready to go.”

Just as well, because he is heading back to London this weekend as part of another Scottish side that is looking to defy the odds.

Saturday’s Champions Cup quarter-final will be the sixth time English champions Saracens have met Glasgow Warriors and their eighth meeting with Scottish opposition in all in this competition. The reigning English champions are yet to be beaten and they come into this match with a season-long unbeaten record in all competitions at Allianz Park.

Johnson admits that it would have been difficult for a Glasgow team which contains so many Scottish internationals, to have persuaded themselves that they could beat a team laced with current England internationals had the pattern of play of the first half hour at Twickenham, when the home side registered 31 points before Scotland started the astonishing rally that saw the match finish level at 38 all.

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Instead there is no lasting psychological damage for those who became the first Scottish team to retain the Calcutta Cup for 35 years and they can now move on to this new challenge.

“If we were to lose like that, with how it was going it would be pretty devastating, but I don't feel that way because we came back,” said Johnson.

“I know there are a lot of Glasgow boys with Scotland and England guys at Saracens, but this is a different game, a different week and we've got past that. We are aware of the challenge ahead and we're ready to go there and give it our best crack.”

Having communicated brilliantly with Finn Russell in giving him the shout that let him exploit that opening and come so close to producing the unlikeliest Scottish victory in sporting history, Johnson had a post-match chat with his former Glasgow team-mate that offered further encouragement in terms of getting to England’s captain Owen Farrell, who had arguably his worst half hour in Test rugby as Scotland mounted that recovery at Twickenham.

“I was talking to Finn after the game…. the best 10s in the world, when they get front-foot ball and time to play they are the best players on the pitch, but if you can get up off the line, shut them down and get into them then that creates pressure,” he observed.

“But Owen is a great player. He's world class. I envy the way he plays a lot. We are aware how hard the challenge is going to be.”

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As to the task as a whole, there is full recognition of what they are up against this week, but that recent evidence means Glasgow and their supporters will make the trip with more reason for optimism than they might otherwise have had.

“We are aware that Saracens have been one of the best teams in Europe consistently for three or four years so we know the challenge ahead, but anyone on their day... the England – Scotland game, for example … anyone can go out there,” said Johnson.

“The big thing this week is our physicality and to achieve that we’ve got to go in with the mindset right. The forwards have been hitting each other a bit harder to get to their level of physicality, because you want that to be your mindset going in.”

Get that right and Glasgow know they have what it takes behind the scrum to generate the points necessary to turn the quarter-final seedings on their heads.

It may be unlikely, but stranger things have happened… as Sam Johnson has better reason than most to remember.