WHAT was Celtic’s best piece of business during this transfer window? Adding the physicality and poise of Olivier Ntcham to complement and provide cover for Scott Brown in the midfield area? The deadline day move for PSG striker Odsonne Edouard? Persuading midfielder Stuart Armstrong to forget about the Barclays Premier League and pledge another 12 months to the club? Or convincing Patrick Roberts to defy Pep Guardiola and sign up for a second loan spell? Just perhaps the correct answer is in fact none of the above. Perhaps the real coup the club’s front office pulled off this summer was still having ownership of the burgeoning talents of Kieran Tierney when September 1 ticked round.

So far this season, after all, the 20-year-old has become the second youngest captain in the club’s history, rattled in a goal of the season contender against Kilmarnock and generally picked up where he left off as one the most promising players to come out of the Scottish game for many a year. Roberts himself certainly wouldn’t seem to disagree with that analysis, and not just because of his friendship for the Celtic youth academy product, whose affection for the club seems to have rubbed off on him.

“When I first came in Kieran was one of the young lads breaking through,” said Roberts, after his second coming at the club this week. “For his age, his experience and maturity, this past year has been incredible. Obviously he’s been skipper a few times this season as well and that will make him more mature and a better player.

“His goal against Kilmarnock was a screamer,” the Englishman added. “Obviously the game wasn’t on the TV but I saw the highlights and I was blown away. He was captain as well, so he texted me as he was absolutely over the moon about it. He said he’s never hit anything better! So I think I’ll need to try and match it this year.

“He is right up there - right now his potential is incredible. He’ll have a big future in the game I’m sure and he’ll go to the very top. You see things in the media all the time [about clubs being interested] and some things are real and some things are fake. But the reality is he’s an exceptional player and big clubs will want to look at him.

“But there’s definitely no rush for him to move on, he’s playing games and scoring goals and enjoying his career. He’s a Celtic lad, he wants to play for the club, he just wants to play as much as he can and enjoy it.

“He’s getting better each game. That’s most important, I know it’s a job but young lads play this to enjoy it. He’s a fan, he’s watched players come and go at Celtic and he’s wanted to be like them. He’s lived that dream. He loves the club, I think he’s got Celtic duvets ... he’ll kill me for saying that.”

Aside from a fine goal at the Etihad against Manchester City, Roberts hopes to improve on a Champions League campaign last season in which he made only a peripheral impact. First up is the chance to renew acquaintances with the most expensive player in football, Neymar, when Paris St Germain arrive in Glasgow on September 12. Roberts will hope for better fortunes than last year’s season opener, when he spent most of his evening in the Nou Camp vainly chasing the brilliant Brazilian around the pitch.

“I don’t think I touched the ball much, I was running back following Neymar,” said Roberts. “This is the kind of teams you’re up against, this is why it’s the best competition in the world and this is what all the players want to play in. It’s the best competition and we want to do our best in it.

“He was playing on the left and I was on the right, so I’ve got to help my full-back out against the most expensive player in the world,” he added. “But it was a good experience, one you take on and strive for. You want to be playing at the top level, so you’re not chasing back. We’ve got more good experiences to come in the Champions League. His price is incredible but it’s the way football is going.

“I recall that after Borussia Monchengladbach away the manager said the first year was to learn what the Champions League was like, as it was a couple of years since Celtic had been in it,” he added. “This year hopefully it can be a bit different, we’ll be more experienced and ready for the Champions League. Obviously, being invincible and winning the treble is a significant thing, especially as it’s not done often. I think we can go into the Champions League more experienced and with the quality of what we achieved last season we can bring that into the Champions League. The manager is the type of manager that plays to win and to show his style of football obviously on the biggest stage.”

One of the fringe benefits of that exposure to Champions League football is how this young Englishman can help his ‘dream’ of getting into Gareth Southgate’s national squad. “England squads are normally picked on current form and how people are performing for their club,” he said. “Internationals are every other month and it’s how you perform for your club. I want a consistent season, playing well, scoring goals and enjoying my football.

“Of course, I’m English and my dad, mum and brother would love me to play for England. That is obviously the dream, to play for the senior team. I can only do that by performing week in, week out and for me the best place to do that is at Celtic, to learn here and improve here and that can hopefully take me onto the international stage.”

Roberts might not have had Celtic duvets but he did have Celtic strips as a child, even if the boyhood Liverpool fan would never have imagined how much this club would take hold of him. “When I was younger I had strips because I liked the colours, green and white. Maybe that was an early sign of me foreseeing my future.”