Jens Haas still remembers the first time he suspected his schoolmate Jurgen Klopp had the mind of a football manager.
They were 11 years old, being driven to play football for SV Glatten's youth team, listening to their beloved Stuttgart's latest Bundesliga match on the radio.
Young Jurgen began to analyse Stuttgart's tactics - and suggested a couple of substitutions to alter the course of the game. Moments later, the commentator confirmed that Klopp's suggested switches were being made.
"I was amazed by his knowledge and understanding of the game," recalls Haas. "Sometimes I thought he was already a coach."
Klopp's school days in the Black Forest offer the first clues as to how he grew up to become the ultimate modern football manager.
He is revered at Mainz, where he went from player to head coach overnight and took the club into the Bundesliga for the first time; at Dortmund, where he toppled Bayern Munich; and now at Liverpool, with a sixth European Cup and a march towards a 19th league title before coronavirus intervened.
Equally at ease with players, fans, executives and journalists, this smiling, gesticulating, bear-hugging coach seems to embody these clubs whose supporters demand an emotional investment from the man in control of their dreams.
There's plenty more on Klopp's personality and methods to come as we speak to some of the key figures in his journey to Anfield. The story begins in Glatten, the idyllic Black Forest spa village where he spent his formative years.
We meet Haas opposite the bakery, beside a fountain that flows into the River Glatt from which the village takes its name. This is where Jurgen, Jens and their SV Glatten team-mates would gather before travelling to away matches.
A short stroll along the river's grassy banks, where the boys used to ride their bikes, takes you to Klopp's childhood home, a large white-fronted house where his mother still lives, opposite the shiny new town hall and less than a corner kick away from the primary school that Klopp and Jens attended.
It is here, among the hills of Swabia - a land of cuckoo clocks, traditional costumes and hearty foods in south-west Germany - that Klopp developed his sense of freedom, a far cry from the industry and intensity of Mainz, Dortmund or Liverpool.
"People here are very quiet and solid," says Haas. "They are cautious with money. They like to work and they judge people on what they do.
"Swabian people take a little while to warm up, but once you are friends you are friends for life. It's a really good place to grow up. You have time for yourself and you can focus on what you want to do."
Klopp has two older sisters who he says were like second mothers to him, but it was his father Norbert - a travelling salesman and former amateur goalkeeper - who encouraged him to take up sport.
"Norbert had a big influence on him, he shaped him," recalls Klopp's first coach Ulrich Rath, who founded the Glatten Under-11s team in 1972 so that his two sons Ingo and Harti could play for a team alongside Klopp and Jens.
"It's important to know that Norbert Klopp wasn't born here in Glatten. He's from Rhineland-Palatinate, close to Mainz. The people from that area celebrate carnival. In Glatten and in the Black Forest, we don't," he adds.
"Norbert was very active here in this club, first in football and then later in tennis. And Jurgen got his father's eloquence, enthusiasm and vigour.
"His mother is originally from Glatten, from a long-established family. The people from the Black Forest are quiet, laid-back people. They always had to work hard. They were always strong-willed.
"When Jurgen is jumping up and down, I can see Norbert in him. But when he closes the door behind him at home, he finds peace and quiet and collects his strength. That's his mother."
Klopp was a midfielder and captain for SV Glatten's youth teams until he switched in his late teens to TuS Ergenzingen, a bigger team in a town 15 miles away. Rath describes him as a "bad loser" but a "natural leader".
"He was always right at the forefront and he spoke up when something was not right," says the 79-year-old Rath. "We had a good relationship. He was ambitious. And he would always tell his team-mates 'Let's go' and push them."
The pitch where Klopp used to play has tall pine trees along one touchline and a stream along the other, from which Haas remembers retrieving many a stray ball.
In 1981, matches moved across the village to a new sports club, where the yellow and black colours of the local team are an uncanny match for those of Borussia Dortmund. A photo of Klopp in his Dortmund prime, signed and dedicated to the people of his home town, sits proudly among the other trophies and memorabilia.
This was also the venue for a celebration to honour the village's most famous son when Klopp led Dortmund to the Bundesliga title in 2011.
As the cheering and chanting subsided, Klopp went on stage to make a speech before mingling with the people of his childhood home.
"It was amazing," says Haas, over a local wheat beer in Glatten's nearest thing to a sports bar, a smokey wooden den with TV screens where the local bikers' club have taken up residence for the afternoon.
"One minute he was the professional coach of Dortmund and then the next he was an old classmate. He was interested in the village, in who everyone was, and he spoke to people in the local dialect."
Rath rarely sees Klopp these days but becomes emotional when he recalls a surprise phone call from his former pupil on his 75th birthday.
"He congratulated me and wished me all the best," says Rath, choking back tears. "This is his home. And he has never forgotten that."
After leaving Glatten, Klopp played for several amateur clubs, including Rot-Weiss Frankfurt, while studying for a degree in sports science at the city's university.
In 1990, at the age of 23, he moved 30 miles west to sign a semi-professional contract with second division team Mainz 05, under the watchful gaze of club captain Michael Schumacher.
"Klopp was a typical student at this time, in both looks and personality," laughs the 62-year-old, sitting in a corporate suite at Mainz's new 34,000-seater stadium, a gleaming symbol of the club's dramatic rise under Klopp's management.
"He was always wearing jeans and a T-shirt and was really easy-going with no stress."
Life on the pitch was to prove rather more traumatic for Klopp, who has always confessed to having second division legs but a first division brain.
"When he came to us he was a forward," adds Schumacher. "He was fast and good with his head but he struggled with the technical side of the game.
"It was hard for him. When they announced his name, the fans would whistle and boo. I remember after a game we were sitting in the hydro-massage pool and Klopp said to me 'What can I do? The coach always wants to bring me on.' He knew he wasn't the greatest player, but he did what he was told."
A switch to defence under the tutelage of influential coach Wolfgang Frank turned the 6ft 4in Klopp into a success at Mainz, where he played 325 games in a decade-long career. But it was the sudden decision to install him as manager that really brought out his strengths.
Mainz were facing relegation to the third tier of German football when president Harald Strutz made the bold call in February 2001.
"The situation was that we'd gone through three managers in quick succession," says the affable Strutz as he looks out across the pitch at the creaking Bruchweg Stadium, Mainz's home during Klopp's time as player and coach which now serves as their training ground.
"We had a very important game and we said if nobody is here to help the team, they have to do it themselves.
"Jurgen Klopp was full of passion, a normal man with a special personality. You could see in all the games that he was a leader. You could see the supporters were so impressed with his personality.
"We decided to make him the manager and that was such an explosion of emotion for all the people living in this city. And it started the greatest time for this club."
The impact was instant. Mainz beat Duisburg 1-0 in Klopp's first match and won six of their first seven games to pull clear of the relegation zone. Better was to follow.
In two successive seasons, the club challenged for promotion right up until the final day of the season, only to miss out in agonising circumstances both times.
While lesser men might have cracked, it was the way Klopp galvanised the club and the city that so impressed Strutz.
As 15,000 fans gathered in front of the theatre in Mainz's main square, Klopp spoke from the heart.
"Everyone had tears in their eyes, but Jurgen got on the stage and told them we would come back stronger and try again. It was so impressive for all the people to see such strength. He always found the right words."
Tears turned to joy the following season when Mainz secured their first ever promotion to the Bundesliga.
"I can promise we had a beautiful evening," says Strutz. "Jurgen always tells me he has this image of me that he'll never forget. Standing in a pub at 3 o'clock in the morning looking so happy. Smiling, laughing, drinking."
Mainz spent three heady seasons in the Bundesliga, ample time for Klopp's tactical acumen and infectious charm to make an impression on one of the most powerful men in German football.
"When you had to play against Mainz, on the one side the players were not very good, but on the other side it was so difficult to beat them because they had a lot of spirit," says Hans-Joachim Watzke, the chief executive of Borussia Dortmund.
"For the general public he made a real impression during the World Cup in 2006 when he was an expert on TV.
"For the Germans it was a new thing that this guy had such a high competence for analysis but also made it entertainment with a lot of charm. It was fantastic."
After more tears as he said farewell to the fans in Mainz's main square, Klopp joined Dortmund in 2008 and immediately formed a close bond with the club's impassioned 'Yellow Wall' of fans at their 80,000-capacity Westfalenstadoin.
Playing his trademark brand of "heavy metal" football while screaming and gesturing from the outer reaches of his technical area, Klopp turned a struggling Dortmund side into one of European football's most thrilling sights, storming to the Bundesliga title in 2011 and following it up with the league and cup double in 2012.
"He gave the team a new spirit," says Watzke. "He played another style of football to what we played before: aggressive, pressing with power and with his empathy on the side.
"The fans and the players loved him from the first moment. The whole city, the whole region was out of control."
Klopp's superstar status is encapsulated in helicopter camera footage of the culmination of Dortmund's title-winning parade in 2011. With the newly-penned 'Kloppo du Popstar' anthem blasting out from the speakers, Klopp emerges through a cloud of smoke, dances onto stage in aviator shades, boots a ball into the crowd and waves to every adoring face.
"He's one of the most famous men in Germany," says close friend Uli Graf, the writer and producer of 'Kloppo du Popstar', which reached number two in the German charts.
"But he doesn't want to be a pop star. He is a man of the people - the boy from the Black Forest who became a hero."
Graf describes holidaying with Jurgen Klopp as "the biggest fun you can have".
"You'll be laughing, joking, you can talk about politics, sports," he says. "He is a very intelligent and clever man, you don't have to fear what you say."
A great football coach, a decent dancer and an ideal holiday companion. But Jurgen Klopp's talents don't end there.
If ever a Borussia Dortmund sponsor was wavering about renewing their deal, they would receive a personal call from Klopp himself.
"Jurgen Klopp is a marketing man's dream," says Carsten Cramer, who was head of marketing during Klopp's seven years at the club and is now managing director.
"A person like him working for an emotional club like Borussia Dortmund was a perfect fit. He was able to give this club and its identity a human face.
"He is a weapon, a perfect all-rounder and he supported us in an awesome way. The sponsors were so touched that the manager of Dortmund was calling them that they all extended their deals."
Five years on from another tearful parting of the ways, Cramer and Watzke remain close friends with Klopp and were guests in Kiev and Madrid for both of Liverpool's Champions League finals under the German.
"If you work together with a person like Jurgen for seven years it would be a lie to say you don't miss him. He's an extraordinary person," says Cramer.
"But to see how he gives hope and power not only to Liverpool Football Club but also to the city makes us very proud."