"I'm looking forward to the penguin party. The penguin party was what sold this whole ridiculous idea in the first place—that and getting a medal with a polar bear on it. Ever since I was awarded a yellow ribbon at the Eisteddfod when I was nine, I've always been persuaded by the promise of a prize. My ribbon was for reciting a poem about a fox who ran over the hills. Whenever I see one now, which is surprisingly often in the city, I always think of how ‘he disappeared in a flash like a falling star'. I am most certainly not doing anything in a flash. But I have hugged a husky, had my photo taken with a yeti, and been cheered by the Bishop of St Paul's Cathedral, so today is probably going to be one of those 'good' days - later, when it's over, and my knees have stopped hurting.

Nine-year-old me would have no problem with any of this and would have whizzed round the whole course high fiving the huskies and dancing to the jazz band. Fifty year-old me is currently thinking this is one of my more daft ideas - run 10km around the streets of London on the coldest February Sunday since 1864. I am sure the BBC right now is saying it is very, extremely cold even for February, followed by an amber warning not to run, I lost the feeling in my fingers in Trafalgar Square, and I am sure my toes will have dropped off by Covent Garden. Surrounded by lycra and sweat, I am so far out of my comfort zone I am not sure we are on the same continent. My new normal seems to be my discomfort zone.

I wish I could remember the exact moment I decided I had had enough. When being fat and uncomfortable wasn't comfortable anymore. I wish I could tell this as some dramatic story about a life-changing diagnosis, an ugly breakup, or that some wise guru spoke to me in dream that could become the plot of the latest best-selling self-help book. Think Eat, Pray, Love, but with more Bedfordshire rain than Bali sunshine! It was much subtler than that. It was a constant gnawing sense of disappointment in myself, a feeling that I was flawed and fat and faulty. A feeling that I soothed for years with tubes of pringles, jammy dodgers, and vegan kebabs from the local takeaway. Yes, such a thing exists, and they are marvellous!"