Running has been a big part of my life for many years. It has been a fix, a punishment, a distraction and a focus. In darker times, I would run at a rapid pace through the streets of New York, where I used to live, feeling the burn in my chest from too many cigarettes the night before, the thumping of my heart from too much cocaine and the sweat on my brow from too much booze. I wanted it to hurt. I wanted to hate myself, to teach myself a lesson.

At other times I would run to try to avoid that part of myself in the first place. I clearly remember waking up on my 31st birthday, a week before I finally gave up booze, and running 20 miles so that I wouldn’t have the energy or desire to get hammered again that night. It didn’t work. I had to leave my own birthday party before half of my friends had even arrived because I was throwing up on my shoes. It was still light outside.

But when times were tough, running did a pretty decent job of lifting my spirits, allowing me to think through a problem or have an hour away from gnawing guilt, panic-inducing stress or overwhelming depression. Signing up to marathons and half-marathons gave me a focus and a routine: eight weeks or so off the fags and booze while raising a few quid for charity and being a Good Person. Sure, there were weekends during the training period when I fell off the wagon spectacularly, and I would always appear at the start of the race less prepared than I wanted to be, but it kept me away from the demons that occupied my mind when I was drinking regularly, the suicidal thoughts, the niggling conviction that life was not worth living.

Then, at the beginning of in September 2017, and now living in London, it all got too much. After a summer of sort-of training for the Loch Ness marathon and drinking myself into a dangerous state of depression, I admitted defeat. I sought help for my drinking, through a 12-step recovery programme, and ran my first marathon a few weeks later in sobriety in beautiful Inverness. It ended up being the fastest I had ever run.

The fact is, I have an obsessive all-or-nothing personality, and a capacity for mental, physical and emotional pain that is not uncommon among addicts. That, combined with a love of running and the countryside, probably made my next move inevitable. I’m certainly not the first addict who has turned to endurance sports to get their kicks.

So I signed up to an ultramarathon. Race to the Tower is a double marathon along the Cotswolds Way via slippery forest trails, up and over hills that, added together, amount to the equivalent of 7,500 feet in elevation. It’s not the first time I have entered an ultramarathon which, for clarification, includes any distance over a marathon, normally 50km (31 miles) or above (a regular marathon is 42km or 26.2 miles). I have backed out of a few over the years with various excuses.

This time I trained like my life depended on it, which, frankly, at times it did. Sixteen weeks of graft, of huge mileage, of hills, of lifting weights, of pushing my limits – I loved it. The focus, the purpose, the progression, the hours on end lapping Hampstead Heath in London. I fell in love with the mental and physical space, the weird calm that comes with knowing you have nothing to do but put one foot in front of the other until the mileage is done.

The day of the race is one I will remember for ever. The route itself was breathtakingly beautiful and the steady pace required meant that it was OK to stop and take photos; it was possible to run with a fellow runner for an hour or two, to swap life stories and speak honestly about how we were feeling, to reassure one another we were going to get through this. There was none of the jostling and elbow barging of a city marathon, none of the overwhelming clatter and clamour and crowding of the better-known races that, secretly, I have never really enjoyed.

Around 35 miles into the race, almost seven hours after starting, something happened. I took stock of the pain and discomfort I was in and realised that it wasn’t going to get much worse. I understood that if I could sit with the aches and the exhaustion and just keep moving, then I would make it. I will never forget that moment. Knowing that I could do it, that it was in me, that if I stopped fighting and started enjoying the mile I was in, then I was unstoppable.

I completed the race in 11 hours, the 8th-fastest female across the line. But there are no numbers to explain what it means to have done it; what it took to get to the start, never mind to finish it. I realised that I am capable of more than I ever thought was possible, as long as I stay focused on the mile I am in and keep moving in the right direction, away from the way things were.