David Weir is a veteran of the Paralympics, and it shows. He is 33 years old, but the wheelchair racer speaks with the wisdom and thoughtfulness of a much older athlete. He has packed a lot into the years since his first Paralympics in Athens 2004: silver in the T54 100m and bronze in the T54 200m in Athens, golds in the T54 800m and T54 1500m in Beijing in 2008, plus silver in the T54 400m and bronze in the T54 5000m at Beijing. He has won the London Marathon six times since 2002 and holds every British record at all distances up to 5000m and at 10km, half-marathon and marathon.

Weir isn't just fast – he's fast over almost any racing distance. Over eight punishing days in London he will defend his 800m and 1500m titles and challenge for gold in the 5000m before attempting to finish the Paralympics in a blaze of glory in the marathon on the last day.

How does he stay motivated? "It has got tougher over the years," he says. "I had a big tick list of achievements that started from Athens, I wanted medals, world records, marathons – the last one was New York 2010 – and I won that. It has been tough because of the motivation – what else have I got to do?How do I get faster?"

Earlier in his career Weir, who was born without the use of his legs, could win races easily, with clear distances between himself and the opposition. The competition going in to London will be much stiffer, he insists. "There are not days when I can win a 1500m by 20m anymore. The entire sport has changed: everyone has gone professional, the training methods are different, the sports science and technology is different, and you really noticed that in Bejing. Lot of nations have got stronger."

But, adds the Londoner, in these games he is very much on home turf - an honour that provides vital motivation. "These are exciting times," he says. "It's exciting for me to race as a Londoner in London. It's one of those things you dream about when you are younger."

Weir could leave these games as one of Britain's Paralympic heroes with medals in four events. But it will not be easy. He faces stiff competition from rivals Australia's Kurt Fearnley – who took gold in the 5000m in Beijing – and Marcel Hug, the 26-year-old Swiss racer who took home no medals from Beijing but posted new world records in four distances in 2010. The three men will go wheel-to-wheel in the 5000m on Sunday [2nd sept].

Weir appears undaunted, saying that he is in the form of his career, managing to remain injury free and in good health after a series of competitions where he struggled with injuries. "You have to be mentally strong. When I was young I used to compare myself, but now I don't," he says. "I'm really nervous, if you don't have nerves you shouldn't be there. But I go in and I think – they are scared of me, they are trying to work out what I am doing. In training, I cover every point they are good at and every point I am good at – so I don't miss anything. So hopefully that should win me medals."

If there were need for further motivation it has come in recent days in the guise of a barb from the para-cycling world champion Jon-Allan Butterworth, who claimed cycling took itself more seriously than track and field, delivered more medals — and should get more funding.

Weir's repsonse is restrained, but firm. Results at last year's world championships in New Zealand – where Britain won 12 gold medals – were evidence that £6.73m of investment was bearing fruit, he argues. "At the world championships, it wasn't just me who won gold medals, it was seven or eight others. It showed we've jumped up another level and showed the world we're still a force in athletics. He probably said it at the wrong time but at the end of the day that's his view."

Weir clearly sees himself as a driving force in that development. Having started competing when he was only eight, he originally wanted to be a basketball player – but there were no teams in South London. "I played a game of basketball and I did a race, and got more of a buzz out of the race so that's what I stuck to," he says. "I think I made the right decision".

Weir is a patron of the 2012 London Youth Games and coaches young athletes, including the 18-year-old protege Jamie Carter, who will compete in the 200m. "It's looking good for the future and that's what I really want to do, tour the country and get these other wheelchair racers on board," he says. "I want to get these kids to Rio and beyond."

But getting to Rio himself is something he is not willing to commit to just yet. The strain of his punishing training schedule is plain. "I'd like to have this winter off, I just want a normal Christmas with the kids, just have that nice glass of wine and eat that cake and not worry about getting up for training on Boxing Day and training New Year's Day," he says. "I just want to be a normal dad over Christmas. And I will make my decision after that."

For Weir, this Paralympics is not so much about highlighting issues faced by disabled people – he thinks that battle is well on the way to being won – but about demonstrating the value of top-quality disabled sport. "Maybe we have to prove a point to the sporting world that we are fantastic athletes and we are worthy of watching or sponsoring," he says. "After Beijing we saw a lot of kids wanting to try wheelchair racing, and hopefully after this games you'll see another big boost.

"It will inspire any disabled person who wants to try it at any level, even if it's just to keep fit. There is not that barrier anymore."