The man with the biggest grin in the Premier League leans back on a sofa and talks about the days when there was not quite so much to smile about.

Released after a year at Hamburg in Germany, Son Heung-min was 17 and sitting in a single room in a Portsmouth guest house.

He had a dream of playing football in Europe and he had some talent. But back in 2009 that was about all he had.

Tottenham star Son Heung-min spoke exclusively to Sportsmail about life on and off the pitch

The 25-year-old has come a long way since being released after a year at Hamburg aged 17

Yet, the South Korean is a picture of delight as he continues to take English football by storm

'Yeah, I had no friends there, no family with me and I couldn't speak the language,' Son said this week. 'I didn't know a single word. I was on my own and I was scared, you know. It was tough.

'I had a trial at Portsmouth and one at Blackburn, too. They put me in a guest house. But I was a kid and I didn't know anything. So that is my first memory of England and it is a bad one.'

Today at Tottenham they call him 'Sonny'.

It is appropriate. South Korea's most high-profile footballer lights up rooms the same way he lights up football pitches.

Tottenham's improving season already has Harry Kane's name written on it but Son -with his direct, eager running and thundering goals - has found a bit of the limelight, too.

Son's direct, eager running and thunderous goals have endeared him to the Tottenham fans

Asked if he finally feels established, he smiled and said: 'I try to be but I don't think so. Harry and Dele (Alli)... I just tell people that I play with them... that's enough for me.

'All I do is practise every day, every session, and hope to learn. Look at Harry. I watch him train and he scores from everywhere, it's ridiculous. I want to be at that level and I have done some OK things.

'I have scored some goals, but that is not everything, is it? Football is more than that.'

The day we meet has already been a long one for Son. Training is always energetic under Mauricio Pochettino and that has been followed by an hour or so of commercial work for the club. Briefly, he looks a little weary as he wanders in.

But his mood brightens quickly as he begins to tell his story in excellent English, delivered with a hint of a German accent - the legacy of five successful years in the Bundesliga, first with Hamburg - where he made the most of a second chance - then with Bayer Leverkusen.

Harry Kane is someone that Son aspires to be like - due to his devastating finishing prowess

'When I went to Germany, all I knew were German swear words,' he said, laughing. 'I learned them on purpose before I got there. I was 16. If someone says something bad to me, it's no good if I just stand there and smile is it? So I can swear in German, English and Korean!

'It's not a good thing, but I think when I joined Hamburg I had to know how to be.'

There is a story about the first time Son was taken supermarket shopping by his agent in Hamburg and placed only one item in his basket, a tub of hair gel.

That seems at odds with the modest 25-year-old who now appears to be coming to his peak years as a footballer. In South Korea, he is ridiculously famous.

He is followed to every game for Tottenham by a handful of Korean reporters.

When Son moved to Germany as a teenager, the first thing he did was learn their swear words

When he visited Seoul with Spurs last summer, the welcome at the airport was more befitting of a rock star. In his own mind, however, it all looks and works and feels a little different. 'I am not that popular,' he said.

'The skaters in the Olympics at the moment are really popular and they deserve it. They have been doing well and I am very proud of an Olympics in South Korea. It's important for my country. But I am not popular like that. I try to be like so many big players, but I am still a young boy. I have a lot of things to do to be at that level.'

At Hamburg, Son played with the former Manchester United forward Ruud van Nistelrooy, who was a great influence.

His hero, though, is another former United player, the Korean Park Ji-sung. 'I can't compare to Ji,' he said. 'He is a legend and my idol. They are still so proud of him at home.

'It's difficult for an Asian to play in the Premier League. It still is. And he was the one who did it first so it was even harder for him. I am still hoping to play like him and bring fans like him and have an impact like him but I am not there yet.

'He was here and consistent for seven or eight years. I have to aim for that. He played at a club with Rooney and Ronaldo and Giggs and still got in the team...'

Former Manchester United and South Korea midfielder Park Ji-sung is Son's idol

When Tottenham first looked at Son in 2013, he was back at Hamburg and finally catching people's attention. The Premier League club thought Son had talent and could be useful as they tried to expand their commercial reach overseas.

They baulked at the £12million asking price, but two years later paid almost twice as much to sign him from Bayer Leverkusen. 'He developed so quickly in that time,' said a Spurs insider this week.

In north London, Son is now seen as a complement to some of Tottenham's other burgeoning talents. Mousa Dembele has the presence, Christian Eriksen the passing while Son is the dribbler.

Son has scored 11 goals in all competitions for Spurs in a productive campaign so far

This season he has scored 11 goals and it is a far cry from the moment he sat in Pochettino's office in the summer of 2016 at the end of a challenging first season and talked about the possibility of a move away.

'I just wanted to play every game,' said Son. 'I am hungry and I met the gaffer to ask him about playing more. So we talked about the future and he said so many good things.

'When a player has a bad time and needs some help, he will give it. That is why I am here now and doing better.'

In Pochettino's recently published diary of last season, the manager tells his own version of that meeting. 'He wanted to leave after a bad year,' wrote Pochettino. 'We were clear with him that he had to earn the right to play. But I told him he was part of my plans and he decided to stay.'

Pochettino also spoke of Son's entourage.

Mauricio Pochettino (left) persuaded Son to stay at Spurs after his tough first season

'A secretary, the works,' he wrote. 'His father is his agent and he has many sponsors, too. Managing all that isn't easy.' If that sounded a little like a warning, more than a year and a half on from that, Son's mind is more settled.

The Korean greets every team-mate with a different handshake, but has not got one for his manager. 'No, I am too scared to do that,' he said with a laugh.

'I just say, "Good Morning..." That is a respect thing.' More importantly, Son credits his manager with advancing his career. 'He has done so many good things that I can't even say the words,' he said. 'It's unbelievable. Sometimes he has been my coach and sometimes he has been like my family.

'I can't say just one word to sum it up. I am just thankful.'

Son greets every team-mate with a different handshake but hasn't made one with Pochettino

If Pochettino's football philosophy is sophisticated and nuanced, then Son's is more simple. Run and run forwards.

'He has encouraged that in me,' he said. 'Football is about scoring and if you want to do that, you have to go forward. That is what he wants me to do. I don't want to do difficult things, just go straight.

'When I first joined I was not like this. The gaffer taught me a lot about my movement and off the ball I have changed a lot.

'It's difficult to say what he was thinking in that meeting. It doesn't matter now. I am just really happy I am still here. He has made things better. I am really thankful.'

Speaking about Pochettino, Son says he has encouraged him to keep making forward runs

The only shadow that hangs over Son's blossoming career is the prospect of national service.

All men in South Korea must complete 21 months in the army before the age of 28.

Exemptions are usually granted on the grounds of sporting success and Son is said to have been particularly distraught when South Korea's footballers failed to win a medal at the 2016 Rio Olympics.

He could face the prospect of national service in South Korea - unless he is given an exemption

It is just about the only subject Son will not talk about.

The theory is that he fears anything he says may be mistranslated and irritate the authorities at home. During our interview he did hint at the expectation and scrutiny placed upon Korean sport stars. This becomes especially relevant ahead of the World Cup.

'The pressure for the national team is actually more (than at Tottenham) because they expect more of me,' he said.

'Hopefully the pressure makes me better as I am learning so many things.

'But many players from South Korea need to be better to make the team more successful. I am one of those players.'

The forward knows he'll have the weight of South Korea on his shoulders come the World Cup

At Tottenham, Pochettino and his staff are very aware of the national service issue and it is in the minds of the club as they plan ahead.

Certainly it would be a shame if Son's time in the Premier League was to be cut short at the end of next season. For him and for us. His journey here has been long and it is worth noting that the two other players who travelled to Hamburg with him as teenagers a decade ago are now playing in the lower reaches of Japanese and Thai football.

'I was just a bit more lucky than them,' said Son, but that clearly is not true. Those who know him speak of a determinedly positive footballer.

'Going to Germany was tough, just as it was in Portsmouth and Blackburn,' he said. 'Everybody talks about now but nobody thinks about you when you are 16 and leave your country.

'It was bad and a hard decision, the hardest. But I had to make it as those chances don't come every day. I didn't feel ready - and I wasn't ready - but I wanted to play in Europe and one day I wanted to play Premier League. I told myself I had to try to make my dreams come true.'

In London, he embraces his heritage by living with his dad Son Woong-jung and mum Eun Ja Kil

Son has been known to bring Korean food to the training ground for his team-mates

In London, Son embraces his heritage. Living in an apartment with his father Son Woong-jung - a former professional footballer - and mother Eun Ja Kil, he has been known to bring Korean food to the training ground for his team-mates.

'I think they liked it,' he said. At home his mother cooks the dak-galbi spicy chicken dish for which his home town of Chuncheon - 50 miles from Seoul - is famous. 'Mum's cooking is still the best thing,' he said. 'It's very healthy.'

With that Son chuckles. That smile is never far away and one senses it never will be. In terms of a dark side, the search begins and ends at one solitary red card, in a junior game at Hamburg many years ago.

'The guy kicked me twice, so I got up and kicked him back, right across his shin pad,' he recalled. 'The ref was right there, one metre away.

'He sent me off. Red card. It is OK to smile and be nice. But I still want to win.'

Son took part in filming for O.R.S Hydration Tablets alongside some of his Spurs team-mates

Son Heung-min was taking part in filming for O.R.S Hydration Tablets, alongside his team-mates Jan Vertonghen, Harry Winks and Kyle Walker-Peters. O.R.S are the official hydration supplier of Tottenham Hotspur.