Cascais, just west of Lisbon, is like Cornwall with warm winter sun. Golden beaches, verdant valleys, cobbled streets full of seafood restaurants and craft shops.

Yesterday, 2200 triathletes sprinted into its calm bay and swam 3800m out and back to the harbour, cycled 180km through a hilly natural park, around the Formula 1 track at Estoril, east towards Lisbon and back into town. Then we ran a marathon along the coastal cliffs before finishing in the packed central square, with rock anthems and the cheers of a raucous, ecstatic crowd.

It was my seventh Ironman finish and perhaps the most satisfying. After a two-year break from full distance races, you start to doubt your fitness and endurance. But once we were in the fresh (17 degrees) clear sea, with dawn rising across the bay, it became a magnificent adventure, surrounded by these thousands of athletes, flooded with adrenaline and wonder. After battling then surfing the incoming tide I finished in 1 hour 24 minutes.

On the bike, we had calm, sunny – not too hot – weather. Even so, the sharp climbs and even sharper descents took some victims, crashing at tight corners or running into walls. Altogether, 250 out of 2200 starters didn't make it to the finish. 

It was a first run-out for my new disk wheel, which definitely gave me some extra speed. And the Estoril track was a special treat, adding a video-game-like surreality. My ride time was 6 hours 1 minute.

Onto the run and the temperature started rising, the rolling course felt tougher with each lap until finally night fell. Weirdly, as soon as it was dark I ran much faster: cooler conditions, no distractions, the end of the race in sight. I virtually sprinted the final seven kms and sailed down into the cauldron of the finish line for a 4 hours 48 marathon: the best I’ve felt at any IM finish. My total time was 12 hours 32. 

Clare had been on the course all day, taking great pictures and shouting encouragement. She said it was just a wonderful day and I’m glad – that makes two of us. Her tears of joy at the finish line always cheer me up! Thank you darling Clare and thank you Cascais for the most fantastic experience.

I often dedicate a race to someone special as I’m going along. This one was for the Queen, because I was sad that she had to go to hospital and, of all British people, she is perhaps the greatest example of endurance and fortitude.