I feel good about it, mate," Mark Webber says as his admirable Formula One career shrinks to just six remaining races. In 12 years as a grand prix driver the 37-year-old Australian has always been the most warm and human of competitors in a cold and often vicious business, so it was hardly surprising that last weekend, after the Singapore Grand Prix, he hitched a lift back to the pits on the Ferrari of his friend, Fernando Alonso, or that he has since received a 10-place grid punishment at the next race in Korea.

Sebastian Vettel won in Singapore, to virtually seal his fourth successive drivers' title, but he was booed on the podium for the third consecutive race as his ruthless decision-making has not won him the affection which envelops his Red Bull team-mate. Their acrimonious relationship has stained Webber's last few years – yet it feels appropriate that he should first voice a different emotion as the end hurtles towards him.

"I'm proud," Webber says. "I know where I grew up [Queanbeyan in New South Wales] and the unlikely scenario of me leaving Australia and coming here [London]. I would never have imagined me ending up having raced in over 200 grands prix with some pretty special wins on the big stage – toe-to-toe fighting all the way. I've got nine wins and 38 podiums. And I've never missed a race. I've never missed a test session. I've never missed an hour in the car."

At the start of the 2009 season, just 11 weeks after he fractured his right leg in a break almost as bad as that which changed the football career of Eduardo da Silva forever, Webber should have used crutches to reach the car on the grid – but he knew "the messaging would've been all wrong". Surely there must have been some test sessions or races he was close to missing?

"I had food poisoning in one race but I still finished it – Fuji in '07. I've also competed with fractured ribs …" Webber shrugs but he's more than just a hard-boiled Aussie bloke who can grit his teeth and growl about commitment and determination. He has carved out an extraordinary life from a distinctly unpromising start. "The numbers speak for themselves. Only three drivers from Australia have ever won a grand prix in 60 years [Jack Brabham and Alan Jones are the others]. So it's not a particularly easy category for us to crack. I've hopefully left a legacy for other Aussies …"

In late June Webber announced his decision to retire from Formula One and join Porsche next year, when he will race sports cars in the FIA World Endurance Championship. He could not disguise his satisfaction when Red Bull, who appeared startled by his choice, eventually appointed another Australian, Daniel Ricciardo, as his replacement. "Exactly. Daniel's on his way now …"

Webber's own route to the peak of F1 was very different to Ricciardo who, at 24, will drive for the grid's dominant team. "When I first came to England in the mid-1990s," Webber says, as he recalls trying to break into Formula Ford and then Formula Three, "I stayed in this box room in Hainault [in north east London]. It was winter and you've got condensation on the inside of the window. It was hard. At the track the other drivers rocked up in fancy cars and you're in your B-reg Fiesta. But that's petrol for your fire."

During those earliest days in his Hainault bedsit, which he shared with his long-term partner Ann Neal, and her then baby son, Luke, did he question his ability to reach Formula One? "I was very doubtful. The first two years in England were on a shoestring. I was getting £43 a day. Our first rent was £550 a month which, bloody hell, was a lot of money. Annie was working hard, but she had Luke as well. Sometimes the groceries were a challenge for the three of us. It was very tight.

"I was so naive. I would go from Hainault station and it was four stops on the tube to the gym. And I didn't have a clue what to do. You're a monkey with a machine gun. Every day you're trying to teach yourself by doing something different. That tenacity and drive helps when you're competing professionally because that's when people tell you if you're doing a shit job. You know what it's like at the top end of professional sport. People change – but I've been lucky. I've had the same people around me since day one. We've had some great highs, some hard lows."

It took Webber 131 races, and eight years of trying, before he won his first grand prix in Germany in 2009. "That first win was probably the sweetest," he says with a grin, "because of the way I won it, from pole, and after a drive-through penalty. To drive away from Seb and win by 30 seconds, in his backyard, was a nice way to get my first win."

There have been so many bitter spats with Vettel, starting in Japan in 2007 when the young German drove Webber off the track while at Toro Rosso. The Australian was furious because, despite vomiting inside his helmet during the race, he was lying second to Lewis Hamilton. "It's kids," he said, "they fuck it all up."

As team-mates the altercations intensified – particularly when Red Bull favoured Vettel. Just before qualifying for the British Grand Prix in 2010, the upgraded front wing of Webber's car had been given to Vettel. Webber still went on to win the race the following day, which, as he said dryly, was "not bad for a No2 driver". Earlier this season, in Malaysia, Vettel flagrantly ignored team orders and overtook Webber to win the race.

"2010 was harder because there was a lot more at stake then. That was difficult to swallow. You put so much into it and you get half a brick put into your backpack. In Malaysia, during those last 15 laps, I did a lot of thinking as to how the whole scenario had got to that point. I wasn't surprised by what Seb did, but just how it had reached that point."

Vettel expressed contrition after the race but at the next grand prix, in Shanghai, he implied he would do it all again. His attitude might be one of the reasons he keeps being booed. "I suppose some of the private discussions that Sebastian and I have had since then have been a bit disappointing," Webber says. "Forget the track stuff. We've had some private discussions and we weren't super-happy with how they went and how we felt about each other. It's tested the relationship to the maximum."

Has the atmosphere improved since Webber announced that he was leaving Formula One? "Not really. We're just going through the professional situation because you've got a lot of people busting their balls for you – the guys working on the car."

Does the 2010 championship still eat away at him – when he led Vettel going into the final race only for the German to win his first title and Webber to finish third? "Yeah. In a way I suppose it would've been better not to have been so close. But I look back at so many races that year of which I was proud. It was a pretty phenomenal year and no one would have predicted that the guy who ended up winning it hadn't led all year. But you always want more."

The only decision he would change, if he could, "would be to have gone to Renault rather than Williams [in 2005]. Renault hadn't won a race but soon after that they ran it. They were like the Red Bull of the time. I would've been winning earlier and had Fernando [Alonso] as a team-mate. So I had to rebuild myself and that took a bit of juice out of me. The fractured leg took more juice out of me in 2008. So I had a couple of really solid uppercuts which took the wind out of me. I also started late, although 24 is probably the right age. Look at [Nigel] Mansell and [Mika] Hakkinen. Those guys didn't start until then. That was normal. You didn't get near a top car. Now, with simulators, the kids are coming in so fast. We've got so many guys on the grid who probably shouldn't be there."

Has nostalgia taken hold as he races tracks like Spa and Monza and Silverstone for the last time? "I think Melbourne and Monte Carlo were really the two where I felt that. I was pissed off I didn't get to the podium in Melbourne as it's the only race where I've never reached the podium – and it's my home GP. It's also where I had my first ever F1 race." Webber finished fifth in 2002 and won those hard-earned points in a struggling Minardi. "Exactly. I must've used up all my Aussie credits then."

Did he know that this would be his last season when he sat on the grid in Melbourne this year? "Yeah. I took all the Aussie and English journalists out to dinner so I knew it was my last race in Melbourne. I think I'll have another moment like that in Brazil [the season finale on 24 November]."

Christian Horner, the Red Bull team principal, was taken aback when he heard about Webber's decision just before Porsche confirmed that he had signed a contract to join them. "My communication with Dietrich [Mateschitz, Red Bull's owner] was always open and very strong," Webber says. "That was important. I never asked him not to say anything, it was up to him how he dealt with that. We'd always had a good relationship and I told him I wanted to stop even if he said there was always a seat for me. Once he'd been informed, then it was good for me and Porsche to get the announcement out nice and cleanly.

"I still feel hungry to finish off the year well but I'm also hungry for the next stage of my career. I've spoken to a few sportsmen, like Pat Rafter, who didn't get their retirement right. You can't hang on if the fire in the belly is dropping. The last few years I've felt it dropping slightly. But the move to Porsche will relight the old fire. Moving into a new work environment, with a different team, will be good."

Webber's continuing professionalism is obvious as, during a day at GEOX, the shoe company who are one of Red Bull's joint sponsors, he cheerfully completes his promotional duties at their Oxford Street store. There is much about Formula One that Webber won't miss, but his familiar enthusiasm is obvious. "I'll miss working with Adrian Newey," he says of Red Bull's brilliant designer who has been the key figure in the team's success for the past four years. "Adrian is phenomenal and when I'm in a rocking chair at 75 I'll still remember how awesome it was working with him. I'll also just miss driving the car and being out there on your own, racing. But the decision is made and, mate, it's the right decision."

GEOX supply all shoes worn by the Red Bull racing team. Go to www.uk.geox.com