Harry Kane has answered every critic and extinguished every doubt. At 33 he is a double winner with Bayern Munich, England’s greatest goalscorer, and sits on the Ballon d’Or throne. On Thursday night, Kane will reach another famous milestone when he surpasses Peter Shilton’s tally of England caps and collects his 126th against Croatia in the Nations League at Wembley.

From the academy coaches at Arsenal who released him aged eight, to the Tottenham coaches who didn’t think he could handle first-team football, to the fans who labelled him a one-season wonder and the pundits who prematurely called time on his England career, each served to motivate Kane. You might think he would finally feel satisfied, vindicated, ready to drop his guard, to take his foot off the pedal, to eat a Twix or two.

Far from it. Kane is speaking to a huddle of journalists at Tottenham’s training ground, back where his career began, and insists he still has a point to prove.

“I don’t think that will ever leave me,” he says. “It’s probably part of what makes me push myself to the limits because in football, you’ve never completed it. No matter what you’ve achieved, there is always a trophy that someone else has won or a goal record that someone else has. There’s always something. Whether it’s noise from the outside, media or the fans or whatever it may be, it just helps motivate me to realise there’s a lot more to achieve.”

Where does that come from? How can the unassuming man who stood on stage at the London Palladium last month, nervously twiddling his buttons and repeatedly sweeping away specks of nothing from his pristine tuxedo, who spent his 12-minute speech naming dozens of people who had helped his career, also be a ferociously driven world-class athlete who carries a kind of burning wrath inside him?

“I think it’s just my mindset, because I’ve had to prove people wrong my whole career. From early academy days proving coaches wrong, proving scouts wrong, it has just been instilled in me. If someone tells me I can’t do something it just motivates me more to do it. Of course, you have to combine the mentality with being able to produce it, so that’s where the self-belief and the training and all the consistent work I do has allowed me to do that.

“I’ve spoken about Tom Brady before and that unwavering mentality to be the best. Maybe with me, because I’m a calm person, you don’t see the ego of some of these great players and I’m a bit more relaxed, but it doesn’t mean that I don’t want it as much as everyone else. It doesn’t mean I don’t put in the work and drive myself and drive everyone around me to be the best.

“Maybe getting released that early and proving them wrong and then maybe proving my early coaches at Tottenham [wrong], just bit by bit, loan moves that didn’t go quite well, again, same thing – ‘I’m going to show them’ – using all the negative stuff as motivation to push me to another level.”

There is something else behind Kane’s drive, a different kind of emotion: the dread of leaving a single stone unturned.

“My biggest fear is finishing my career and thinking I could have done a bit more if I could have just done that or done that. I want to make sure that I cross every bridge so that whenever that day does come, I can say I’ve done everything possible, I have this record, I don’t have this record – but it doesn’t matter, I can sleep well at night.”

Kane can still remember arriving at his first England camp, in the spring of 2015, and admits he felt “nervous and anxious” about being the new guy. Wayne Rooney was the England captain and was the first person to talk to the 21-year-old Spurs striker. “He told me to just be myself,” Kane says.

But as soon as he got on the training pitch, Kane felt a confidence flood through his body. “I felt like this is my comfort zone, I know what I can do, I can score goals, I can even talk and shout – I felt more comfortable in that sense. I remember training really well and feeling like, ‘OK, if I can do it here I can do it anywhere’, and that gave me even more confidence. I just took that into the game.”

Kane replaced Rooney in the second half and scored 79 seconds later with his third touch in an England shirt. He would assume the captaincy from Rooney two years later, when Gareth Southgate embarked on an overhaul of the squad.

“I was talking to Michael Olise at Bayern and I was asking how old he was, and he was saying at the time he was 23 and I thought, ‘Jeez, I was [England] captain then’, and I looked at him and he looked so young! So I don’t think I realised in the moment how young I was to be named captain.

“I’ve always been quite mature, even from late teenage years, always led by example, always done the right things. It felt quite natural for me. I’ve been lucky enough to do it for a long time now, and honestly the feeling of being captain still feels as good as that first moment I wore [the armband].”

Eleven years and 125 games after his England debut, Shilton will present Kane with a special cap to commemorate the achievement. It will be a busy pre-match, with Kane also expected to find time to parade the Ballon d’Or to the Wembley crowd.

Even in Kane’s world, it has been an extraordinary, whirlwind few weeks.

“I think I struggle to take it all in to be honest,” he says. “I think it is just my natural mindset to look ahead. The fact that I had just equalled the record [last month], it was, ‘right, next camp, let’s go and break the record’. Maybe tomorrow will feel a little different, actually breaking the record and being the one that sits alone on top.

“But in this period especially when there are so many games, I don’t think I’ve taken it all in. What’s happened in the last few weeks, I don’t think I’ve accepted it all, I guess. But maybe during the winter break when I’m away somewhere, on the beach, it’ll be a moment to reflect and then really soak it all in.”