Arsène Wenger was in his car, making his way out of Highbury after a game that had not gone to plan. A boy saw him, pointed his finger, and shouted: “Hey, Wenger, I could play for Arsenal!” The manager looked at the boy and replied drily: “Yes, I am sure you could. But the question is: ‘How well?’”

A decade on from the summer of 2004, Wenger sits on the sofa of his office at London Colney and looks back. Generally speaking, it is not his favourite direction. His instinct is to glance ahead. But try as he might, a flush of nostalgia is inescapable. Throughout the conversation about the Invincibles, his warmth for that time and those players shines through.

Arsène, in the Invincibles season the only change to a settled squad you made was a new goalkeeper. Why did you choose Jens Lehmann? I watched him in Dortmund. I liked his attitude, his intelligence, his personality. Then it was quite simple because this was a deal that was made between him and me directly on the phone. Without any agent, without meeting him directly. We had some interesting conversations. [He begins to laugh] You know Jens! Every detail becomes important. So I thought this guy will either be a complete flop or a complete success because he is special in the way he is intense, argumentative, and speaks his opinion. I was really interested. After two conversations I thought, this is the right guy for this team because he is at the same level of motivation and personality as the rest of the team.

The other strategic move came in deciding that Kolo Touré could play centre-back. Is it a sudden idea to try something like that? Yes. I played him in a pre-season game in Austria. We played against Besiktas, and I said to the coach, Mircea Lucescu, who I knew, can you observe my team and can I observe your team? Before the game I asked: “Are you good up front?” He said yes. I said: “OK give me your impression on my two centre-backs after the game.” I played Kolo and Sol in that game. Afterwards he said he was impressed with our power. That is what I wanted to create. I had two turbo trains at the back with immense power. I thought Kolo, guided by Sol’s experience, can work. That was a major move.

It’s an example of your penchant for remoulding players into new positions. There were several in the Invincibles. I had big fights with Lauren, who came many times to convince me he is not a right-back. [He smiles at the memory] I said: “Look, trust me, you are a right-back.” He said: “No, I am not a right-back. I am a right midfielder, and I can even play central midfield.” I said: “But you can make a magnificent right-back.” After a while he accepted it.

Lauren, right, tried to convince Arsène Wenger that he could not play right-back. Photograph: Michael Regan/Action Images

Do you enjoy those challenges, overcoming that kind of resistance? I like it very much because it really tests the personality of the guy as well. It is my job sometimes to find the right position for the players – it is a case of adapting to his physical potential, his physiological potential, and his tactical level.

What is it about you and your coaching ideas that makes reinventing players such a key aspect of your work? I was involved like that for a long time. For example, with Lilian Thuram, he was a right-sided midfielder when I took him and I put him at centre-back. Emmanuel Petit was a centre-back and he played midfield for us. When you make those kind of decisions you have analysed the player in detail, or you are not completely comfortable with the position he plays in. I bought Lukas Podolski to be a centre forward or a wide player but after a while I thought he is only a wide player, not a centre forward. He can play behind the striker but not completely at the top. Sometimes you have to revise your judgment.

That team seemed like a particularly intelligent group, as if this place was some kind of hothouse, a university of football where the smartest came to learn and develop and get smarter? Yes. I must say I have worked at the top level for 30 years and always when you look back with successful teams you always come to the same conclusion: the guys were intelligent. You have players with talent every year, but to achieve something special, first of all you win it by little margins that at some stage of the season become very tight, and you need your players to respond with intelligence to get through these difficulties. You look back and the only thing that strikes you – you can take Henry, Bergkamp, Vieira, Lauren, Kolo, Cole, anybody from that team – they are all intelligent.

Having an ‘intelligent’ group of players was key to Arsenal’s unbeaten run. Photograph: Stuart MacFarlane/Arsenal Football Club

Did you enjoy watching the sparks fly between them when there was an atmosphere of tension and creativity? Yes. They were demanding of each other. They were really strong personalities. In the dressing room it was not always easy. But there was a global positiveness about them, and competitiveness as well. Guys like Sol are demanding personalities.

How do you manage the bigger squad aspect, and keep everyone happy and ready? First of all you give hope always to the players they can play the next game, and the next game is an important one. The most important thing is not to lose communication. To communicate with them, to explain they are part of it. Maybe a bit less of a part than they would want, but more than they think they are. That’s down to the confidence in your honesty, and the distance between them and you. With time you learn to know when a guy needs a talk. It’s the same in everybody’s life. You have an idea of how close or far away you are in the distance of communication with people. Some-times you think in your daily life, at the moment we are not close enough. It is the same with a player. Sometimes you think, I am losing him at the moment, he is a bit out, let’s get him back again. You learn that in time. It demands patience, and making yourself available to do it.

Do you have to create a boundary in terms of your relationship with players? You cannot be a friend. You have to make tough decisions. When you play in a cup final and you have to leave players out, if you are a friend, you cannot do it. You need above all comprehensive respect. That means you have empathy for people and you can’t be scared to show it to them, but they have to know at some stage you will make the decision that can hurt them. They have to respect that, but you have to do that in a way that shows them respect as well. You cannot always explain everything, but they must know when you make a decision it is with honesty and respect.

Players have to know that sometimes you will make a decision that hurts them, says Arsène Wenger. Photograph: Tom Jenkins/Guardian

Considering the cliche in the modern game regarding how you motivate millionaires, was that an irrelevance with this team in that they were self-motivating? I think it’s the other way round. These guys are millionaires because they are motivated. They are motivated because they want to be excellent. There are three kinds of motivation: the intrinsic motivation which means the guy is naturally demanding of himself that he wants to be the best, and he has always that inner dissatisfaction with what he has achieved. Then you have the extrinsic motivation, and that’s the guy who wants to show others that he is the best in there and he will show them. The other extrinsic motivation is the guy who wants to be respected by others for his quality and what he is doing and he wants to show that quality. Too much money can be a problem sometimes but I don’t think that affects the basics of what makes a player. He can lose his way a little bit. But most of the biggest champions have an intrinsic motivation and money doesn’t change anything.

Ashley Cole celebrates winning the title with an inflatable trophy. Photograph: Stuart MacFarlane/Arsenal Football Club

Of the most pivotal games during the Invincible season, the draw at Old Trafford was the closest to a defeat. Given the heat of the situation, what happened afterwards is interesting. How do you react and encourage the players to cope with such a situation? It was especially intense for Martin Keown, who was treated like a gangster. Even his children said: ‘What’s happening with my dad?’ He was touched by that. Not a lot happened really but it was such news. I tried to minimise it with the group. Let them talk. Let us focus. For us what is important is our next game. I must say this was a team that was in some ways difficult because they had strong personalities, but on that front, it was a very easy team to lead because they were all mature, intelligent; they knew what was important and what was less important. Things like that were not difficult to deal with. OK, they had a go at Martin, had some jokes, but overall they were not distracted by that.

Is there a part of you that admired how they stuck up for one another even though you couldn’t come out publicly and say that at the time? Of course. I was very proud to see that. They were guys who were ready for a fight. Sometimes when you want to see the solidity of someone, you think could I go for a street fight with this guy? In this team I tell you we had some. That was their strength, the kind of charisma they had. They gave you the feeling: I have the quality and I know I have it. Charisma comes from the second part – I know I have the quality and I am ready to stand up for it.

Martin Keown was treated like a ‘gangster’ after his angry reaction to Ruud van Nistelrooy’s missed penalty in the ‘Battle of Old Trafford’. Photograph: PA

When you talk about getting the maximum from your team over a season, although you did in the league, did you feel that didn’t happen in the other competitions? Yes, because that year we could have won the Champions League. Three days before we played Chelsea in the Champions League we played Man United in the FA Cup. I did not want to sacrifice the FA Cup, so I thought I would play a team I thought could beat Man United. The game was at Villa Park and I remember Man United on the day kicked us. Reyes got kicked, we lost some players, we lost some mental strength, and three days later we lost against Chelsea in the final minutes of the game. I could see we were jaded. So I think if I made a mistake that season, that was not to sacrifice the game against Man United. Many times the Champions League conflicts with the FA Cup and you sit there and think, What do I do? [He exhales deeply] That season we could have won everything. I tried to do it. We had the squad to do it. We had 16 or 17 players of top, top level.

That week segued into the Liverpool game, which went badly to begin with. In such circumstances, watching a situation like that unfold, do you feel powerless? You are sitting there. The whole season you didn’t lose a game, and suddenly in a week you think you can lose everything. Chelsea were not far behind us in the league at that stage. What was very worrying was at half‑time when you go in the dressing room, I could sense there was no response. The guys were absolutely speechless. You take one disappointment, two disappointments and you sit there 2–1 down … I was really worried. I tried to mobilise the energy. Come on guys, let’s respond, let’s go for it. We cannot accept this. One of the things you need in our job is the special talent, and the special talent turned up with Thierry Henry. Suddenly it was 4–2 in minutes. Thierry made the difference.

How strange was it that winning the league at White Hart Lane turned out to be such a mixture of emotions? Because Chelsea lost, we knew that if we didn’t lose we would be champions. We were cruising, amazing, and suddenly we were back to 2–2. I thought the referee was a bit unfair with Jens. He pushed Keane on a corner when Keane tried to tread on his foot. He gives a penalty and I still don’t understand how he did it. We were champions, but there was nearly a fight between Sol and Jens! It shows you how much these guys were winners. We had to calm them down in the dressing room. It was not euphoria. It was really amazing. “Guys, we have won the Championship, come on!”

Arsenal celebrate winning the title at White Hart Lane. Photograph: Stuart MacFarlane/Arsenal Football Club

Why was it such a struggle during the final four games to stay unbeaten? It was one of the hardest challenges. Most of the time when you are champions the concentration goes, everybody relaxes, and you lose the next game. As simple as that.

Did you give them a big speech to guard against that? Yes. We played just enough in every game not to lose. But everything had gone! I was more stressed in those games after winning the league. Even the final game against Leicester we were down at half-time. I told them: “Look we have won the championship, now I want you to become immortal.” They were thinking: “This guy is completely mad.” What does he want from us? What is he talking about? But somewhere, they started to believe. In the games, even though the games were not convincing as there was no real urgency, we did just enough. We didn’t lose. When we were down against Leicester you could see the response was strong. I had no worry any more.

Could it have only happened when it did? Before the Abramovich money really took hold, the move from Highbury, and then more external investment strengthening your rivals? It was just in time. Everybody speaks of the Chelsea team that went on to win the championship afterwards but in 2004 they already had a super team. Abramovich came in and injected more money, they brought Didier Drogba and Ricardo Carvalho into a team who already finished second. They took over after that. We had Chelsea coming in, Man City later. Look what happened next – now you have Man United not even in the Europa League. You make one or two average decisions and you are out of it.

Was there something that resonated with the money coming in – albeit legally – that reminded you of your experience in fighting the financial doping of Bernard Tapie’s Marseille when you were with Monaco? You feel like you have stones against machine guns. People don’t want to know that. They just want you to win the Championship. It was a very difficult period but as well a very exciting one.

Do you remember what you did after the Leicester game to commemorate this fulfilled dream? I am talking to you about the past, but it’s painful for me to look back, because I am always somuch focused on thinking forwards. It was one of my dreams, to win the Championship without losing a game. [He pauses, breaks into a huge smile and his eyes light up as the next thought occurs to him]: And I want to do it again.

The Arsenal players warm-up before facing Leicester in the final game of the season – a match they won 2-1 to seal the Invincibles tag. Photograph: Stuart MacFarlane/Arsenal Football Club

Extracted from Invincible: Inside Arsenal’s Unbeaten 2003-2004 Season by Amy Lawrence, published by Viking on 23rd October at £16.99 © Amy Lawrence 2014