This Sunday, almost 60,000 people will cross the start line of the London Marathon. I couldn’t be more thrilled I’m not one of them.

While my own marathon era was short-lived – just the one – I hold it accountable for ruining my running life overall. If only I’d listened to advice and kept my output to enjoyable regular jogs and occasional half marathons, maybe I’d still be pounding pavements almost 20 years on.

I look back on my running life with more than a tear in my eye. For almost a decade, it shaped my days and my weeks and took me to places I could never have imagined, from getting up to run through the dawn in foreign cities to racing up and down Primrose Hill before work. My reward was an unrivalled perspective on the city and the office hours to come. I’ve never found a better way to kick off a new day.

What went wrong? I admit that I didn’t start marathon training in an entirely responsible way. I signed up in the new year of 2008, around three months before the marathon (in 2026, more than 1,000,000 people entered the ballot for the London race…).

My first training mistake was to head out on a 12-mile run when I was out of practice. As a seasoned competitor in half marathons (13.1 miles), I knew I could complete this distance, but I hadn’t put my trainers on in a few months and it proved too much for me. My left knee swelled up and I could hardly put any weight on it or straighten it.

Consultant orthopaedic knee surgeon Khalid Al-Dadah told me that knees are particularly susceptible to running injuries because they support so much weight. “The knee can take up to seven times your body weight during day-to-day activities, and this is amplified during running,” he said. He explained that runners can develop “runner’s knee” due to this overload on the joint, but that it’s better to switch to another exercise, such as cycling, than to give up altogether, because a sedentary lifestyle would make our joints even weaker.

Despite my painful knee, I couldn’t back out at that point. Instead, I found a trainer with a “revolutionary” approach to marathon running. Mike Weeks told me that if I focused on building upper-body strength instead of exhausting my legs with long runs, I would improve my fitness and develop resilience without putting too much strain on my joints.

While the majority of marathon training plans seemed to advocate putting in heavy mileage for four to six months and loading up on carbs to use as energy during the race, I settled into three months of weight training and eating jelly, fat and protein under Weeks’ unswervingly patient supervision.

He agreed to train me even though he thinks marathons are bad for our bodies. And he should know: in 2006, he got Jack Osbourne around the infamous Marathon des Sables in the name of making amusing telly. The race takes place across the Sahara Desert in North Africa and participants run seven marathons in seven days.

Weeks, who ran three marathons a week while he was training, said his muscle density dropped away. “You’d have to put a gun to my head to make me run for more than a couple of hours now,” he added. “So many people think running the marathon will make them healthy, and it’s quite the opposite. Many people leave it to the last minute and then think: ‘Sh**. I’ve got to start cramming in.’ Their body is just annihilated in the training. Running for an hour every day puts your body under so much stress.”

On Weeks’ watch, I didn’t cram in the running, but I did train most days. He was more interested in me improving my sleep than clocking up miles. This was in 2008, before our phone addictions and sleep obsession had really entered the culture. He encouraged me to black out my windows with bin liners. My neighbours never forgave me.

After a few weeks, my knee improved and I was able to add in some longer runs, though by the time of the marathon itself, 18 miles was my furthest training distance (eight miles short of the necessary 26).

I enjoyed the race itself, though I may never get over my time of 35 seconds over the hoped-for four hours. When telling people, I like to point out that I had to queue for the loo three times.

Unfortunately, I know I’ll never get another crack at beating my PB, because as soon as the race was over, my running life took a turn for the worse. I tapered off, as advised, and continued with some of the circuit training. It felt pretty cool to be able to do chin-ups. But every so often, I’d end up bed-bound with an excruciatingly painful trapped nerve in my back. Painkillers didn’t touch the sides. Wherever it flared up, I hobbled around, bent double, for a few days until the swelling eased. I know that a lot of people have experienced this kind of disc pain, and if you know, you really bloody know. Simple tasks like washing my hair or lifting a heavy pan were impossible.

The GP was a total b**tard and told me that he would never refer me to a specialist. Eventually, a physiotherapist sent me for an MRI. Coincidentally, I experienced a worse episode than usual a few days before the appointment, when the problem disc in my lower back popped out (official language: extruded). I couldn’t move on one side and a really lovely A&E doctor told me that he wished he could do emergency surgery, but before I could win that privilege, I had to be unable to move both legs.

I had surgery to remove the screwed-up disc a few weeks later. After a long and slow recovery, I’ve never felt confident enough to run further than the bus stop since. Instead, I do yoga, a bit of pilates and amble around with the dog. I’ve never taken to cycling as I prefer kit-free exercise over all that clobber.

There are many reasons to be cautious about running 26.2 miles, from muscle aches to joint strains, to longer-term injuries and heat stroke or exhaustion on the day. But plenty of people manage it without serious injury through slow and steady training and preparing themselves with adequate food and hydration.

In a now-deleted podcast clip last week, Joe Wicks, who is running this weekend, undermined the idea that our bodies need significant fuel and water to get around the route. “I ran a marathon with no water, no toilet breaks and no food, so I don’t think we really need as much as we are told,” Wicks said, to widespread uproar.

When I first started to run, I never thought I’d get round the park, never mind 26.2 miles. But I wanted far more than that medal. I thought that completing a marathon would transform me into a different person: a significantly better person, who never stayed out late partying because the dawn running alarm mattered more.

Given that running 26.2 miles is such a huge physical challenge, it amazes me that by today’s standards, it seems almost entry-level. Who cares if you’ve shuffled around London for four or five hours when people are ticking off iconic ultramarathons and Ironman triathlons?

Weeks has experience in helping Ironman competitors return to fitness after the well-known endurance event. “They want us to train them harder,” he says. “But we get most of them to stop doing any exercise apart from strength training for 10 or 12 weeks. Most of them are so weak it’s unbelievable to think they are athletes in their prime.” With the importance of strength training now ubiquitous in the endurance world, it seems he was ahead of his time.

I must add that I hope everyone taking part has a brilliant run on Sunday. If my back hadn’t given up, I’d still be running today – just maybe not quite the full 26 miles.