Son Heung-min joined Hamburg’s youth academy as 16-year-old in 2008

Behind the endearing smile and elaborate handshakes lurks a man on a mission.

Son Heung-min’s three goals against Manchester City in the Champions League quarter-finals helped fire Tottenham Hotspur into the last four of the competition for the first time in 57 years.

Back in 1962, with the competition in its former guise as the European Cup, Spurs were knocked out by a Benfica side boasting Portugal great Eusebio, and the Premier League outfit will need to overturn a 1-0 deficit against a talented young Ajax team to avoid falling at the same hurdle this time around.

Tottenham’s hopes in Amsterdam, it seems, appear to be pinned on the return of their talismanic South Korean, who was suspended for the first leg in north London last week and in the absence of top-scorer and England captain Harry Kane has become his side’s go-to threat.

Son has scored half of Tottenham’s goals in the Champions League knockout stages this season and his importance to Mauricio Pochettino’s side was underlined by the fact Spurs only managed one shot on target in the first leg without him.

“The game at Manchester City – two shots, two goals,” says former Hamburg youth-team coach Markus von Ahlen about Son’s performance during Spurs’ 4-3 loss in a dramatic quarter-final at Etihad Stadium that saw the visitors progress on away goals.

“You don’t get many chances and you have to have the security to know if you have one chance you are going to make it.”

Von Ahlen is well aware of the back story to Son’s rise to prominence – it is one of persistent hard work, following the unconventional training methods of his disciplinarian father and having the bravery to move to another continent as a teenager in order to pursue his dream.

Von Ahlen worked with Son when he first arrived in Germany as a 16-year-old, having been scouted alongside two other players as part of a link between Hamburg and the South Korean Football Association.

“He was very quick, he scored a lot and he was very open in working with the team and very interested to learn things,” Von Ahlen, who now works at Bayer Leverkusen, tells BBC Sport.

“His father was there also, and every minute he was free his father trained with him additionally – small, easy technical things. He worked every day.”

Son Heung-min celebrates after scoring for Hamburg’s youth team

Son has spoken openly about his father’s impact on his career – from the strict training regimes he implemented on Son and his older brother as children, to still sharing a flat with his parents in London and being told he should not marry until his playing career is over.

Son Woong-jung was himself a professional footballer in South Korea, until injury curtailed his career in 1990 – two years before the younger of his sons was born.

When his boys were not studying – which included trips to a summer school in New Zealand to learn English – Woong-jung would put them through a strict footballing education of relentlessly practising basic skills.

The boys would have to master one attribute before moving on to the next, while Son recalls his father punishing him with hours of keepy-uppies.

Other punishments were harsher.

“I hit my sons a lot because sometimes it’s necessary. I know Europeans don’t understand this though,” Woong-jung told Korean journalist Minhye Park