Only a small percentage of bilateral amputees have been able to make prosthetics an advantage over a wheelchair. They can be very uncomfortable. It's like wearing a pair of uncomfortable ski boots. They are attached to my upper legs by a vacuum effect so they can be very hot and sweaty. It's a relief to take them off.

I don't need [walking] canes to maintain balance.

I use them to divide the effort of walking between what leg muscles I have and those in my upper body. I can walk without the canes around the house and for short distances. Everyday life for me is like a 12-hour workout session, so my arms are bigger than I ever managed when working out four hours a day in Formula One. Driving a racing car is a piece of cake now.

At airports, my legs make the metal detectors go off like a discotheque. It's not a problem in most of Europe because people recognise me and we can share a few jokes. In Spain, they don't care about racing - except for [Spanish Formula One champion] Fernando Alonso - so I have to take my trousers off there.

I was not happy with the prosthetic legs available on the market. I made my own so that I could swim from my boat while on holiday. I used marine brass in the knee joints so that they don't rust. I also changed the foam that gives the leg its shape. The regular material would get water logged and become heavy; I swapped it for a material I found in racing that doesn't absorb water.

I'm racing again [but] not because I need the money.

I am paid - and I should be - but I wouldn't take on a challenge, a commitment, if I thought it was beyond my capability. I still have passion for racing even if I also have interests that a 20-year-old driver [doesn't have] - like a wife, a son, my friends, a nice house and boat, a dog.

After my accident, some people thought my life was over and that I would never race again. It's a challenge just to get me to the track. But, bloody hell, my life was not over. I've won two races now in the World Touring Car Championship, which is one of the most competitive series in the world. Each year, we race at the Macau Grand Prix. A lot of the drivers are guys whose fate meant they did not make it into Formula One.

I race a BMW with special controls that I designed with the team. I have a hand throttle on the steering wheel but I brake using my prosthetic right leg. My braking is basically as good as a complete driver. Somehow I have sensitivity as if my foot still exists. It's the same when I walk - I feel the ground even though the first part of my body is up in the air on the prosthetic leg. The other day I was washing my boat with a hose. I felt my foot was wet, which is strange because I don't have a foot. My doctor explained that my brain processes the data available - perhaps a vibration of water touching my prosthetic leg and experiences from earlier in my life - and gives me the sensation of being wet.

It's difficult to operate the hand throttle in slow corners when the steering wheel is on full lock and my arms are crossed. This was the problem when I drove the BMW Sauber Formula One car last November in Spain [in a few demonstration laps of a car modified for him]. The seat position was a bit of a compromise and my elbow was hitting my chest in the slow corners so I had to drive with one hand. With more time, we could have made the cockpit better. The guys in the team were saying: 'Come on Alex - this is just for a few demonstration laps.'

I would not have achieved what I did in my career if I did not want to do the maximum every time. That's the same for all drivers.

It was great to be back in a Formula One car after seven years. Dr [Mario] Theissen, the head of BMW Motorsport, congratulated me on being the first person with no legs to drive a Grand Prix car. So I said, 'Congratulations on being the first person crazy enough to let someone with no legs drive a Formula One car.'

The team fitted fresh tyres so I could attempt a quick lap time then we had a mechanical problem. It was like eating an ice cream cone and, just before you get to the chocolate part at the bottom, your wife takes it away. My mechanic was so upset that we didn't get the chance [to finish] he was almost in tears - that was very touching.

I wouldn't say I am a better driver than before my accident but I am more adaptable, more mentally flexible. Before, like most drivers, I would be distracted by an uncomfortable seat or some other small problem. Now it doesn't bother me. This is not because I am Alex Zanardi but because I am part of a group that has to learn to do things in an alternative way. We turn need into talent.

Targets and dreams are important. Overcoming obstacles gives happiness. I have to be twice as happy because I already won two championships in the US in the late 1990s and made overtaking manoeuvres that are still talked about. Despite losing 45 per cent of my body and being 40 years old, I am still in racing - and sometimes all the other guys are in my mirrors. When I go to bed I am happy knowing I am doing the best job I can.'