Saturday October 8, 6.55am. As a former prime minister, I should be used to pressure, to big stages, yet I can feel the butterflies. I am in the city of Kailua-Kona, on Hawaii’s Big Island, surrounded by extremely fit, serious-looking people. It is 35C and 90 per cent humidity — more like a sauna than normal October weather for a Finn — but we are not here for a beach holiday.

Rather, we have come from around the globe to take part in the ultimate triathlon challenge, the Ironman World Championship — a 3.9km swim, a 180km bikeride and a 42km marathon, all in one go. The 2,300 participants are from 50 nationalities and all walks of life: professional athletes, lawyers, executives, accountants, managers, teachers, doctors, flight attendants, carpenters, soldiers, and oh yes, me, the politician.

It is every triathlete’s dream to qualify for Kona but no easy feat — amateurs must earn their place by winning points in one of 40 qualification races around the world. For me, this is a once in a lifetime experience.

The cannon goes off and the long day begins. The swim is first and I have heard horror stories of kicks and punches all over the place. Against my political instincts I have placed myself on the left side, out of the worst crowds in the inside lane. I take the first strokes. The water is crystal clear. I can see the bottom, corals, colourful fish, turtles and all. Beautiful — I feel lucky to be here. The nerves are gone.

I get into a rhythm. It feels surprisingly good. Only one kick in the head and another in the chest. That’s less than what I am used to in politics (and I feel no stabs in the back). After 1 hour and 11 minutes I get out of the water — Yes! Four minutes faster than expected.

A quick transition to the bike: shower, shoes, helmet, sunglasses, sunscreen. The key is not to start too fast and blow up, but it is difficult not to get over excited. Thousands of spectators urge you on in the beginning of the course.

I often get asked why I do sports and how on earth I had time during eight years in government. The answer is simple: an hour of exercise gives you two more hours of energy each day. When you are in a high pressure job there are two ways to wind down and relax. One is to open a bottle of wine every night; the other is to exercise an hour each day. I have always believed in the latter, as much I sometimes enjoy the former.

The bike course in Hawaii is as tough as it gets — out to the village of Hawi for 90km and then back. The sweltering heat of the lavafields is one thing, the winds another. The wind direction often changes, and so it does this time. Into the wind going out, into the wind coming back.

After five hours on the bike I start feeling the physical and mental strain. Fortunately I am well prepared for both. I know this will be the toughest race of my life. I need all the grit I have had in politics. No matter how tough it feels, I just have to keep on plodding away.

After five hours and 39 minutes, I have never been so happy to get off the saddle. At an average of 32km per hour this is definitely the slowest Ironman bike ride I have had. Another quick transition: running shoes, visor and off we go. Usually I love the first steps after the bike. Your legs are wondering what is going on — it feels like having to learn how to run all over again. This time is no different, it is just that my legs will unfortunately have the same sensation for the next 42 kilometres.

The heat hits me like a ton of bricks; my legs feel heavy. I know I am in for a long haul, but I stick to the race plan. The key is not to hit a wall. At every aid station I do the same thing: shove my head into a bucket of ice, put handfuls of ice into my race outfit, grab whatever food and drink is available.

My legs become logs. I am barely able to run, it’s more like a shuffle; one step at a time, both feet never off the ground at the same time; one kilometre to go. “Come on, push”, I tell myself. I know I will make it. Still smiling. I take a right turn for the final 500 metres.

A friend of mine gives me the Finnish flag. I grab it and start running towards the line. The noise from cheering supporters is phenomenal. The professionals have passed a long time ago, but the crowds are still there.

I stop at the finishing line. I hear the announcer shouting something about the former prime minister of Finland. Then I hear the four words I have been waiting for all day: You are an Ironman!

My time is 11 hours and 13 minutes, about 45 minutes more than I expected, yet I have never felt better. I go to the recovery area and see a whole bunch of happy, but tired faces. No more tension, no more nerves, just fatigue and joy.

Later, I get together with some friends for a meal. Then it’s time for ultimate decadence: the huge Cuban cigar I brought with me, and perhaps a glass of vintage red wine.