It is with a cold conviction in his voice that Ronny Deila declares his belief that Kieran Tierney will climb to the top tier of the footballing world. “I am as sure as I was with Virgil van Dijk that he is going to make it,” Deila says. “To take it to the highest level you need something special and these players are special.”

The former Celtic manager saw the talent early, taking note of this spotty teenager who would approach every training session as if it were the first minute of an Old Firm derby. Tierney had a competitive edge that could not be suppressed and, before long, the club’s established first-team stars were doing their best to avoid him on the training pitch. “People did not want to play against him,” Deila tells Telegraph Sport. “He was so aggressive.”

It was clear then, even in those first few days of Tierney’s senior career, that his footballing journey would one day take him above and beyond his beloved Celtic. Four years on from his first-team debut, Tierney’s passion for his boyhood club has not faded but the time has now come for one of Britain’s most exciting talents to embrace a new challenge. Arsenal have been long-term admirers and, after weeks of negotiations, have finally concluded a deal worth around £25 million for a player who they hope will provide the mental edge they so desperately crave at the Emirates.