Journalist Helen Croydon swapped cocktail bars for running shoes a few years ago and is now a triathlete. In an extract from her funny, honest memoir, she shares what her first ever 10 mile run was like

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Four years ago, self-confessed party girl Helen Croydon didn’t even own any flat shoes and was  more likely to be found on a dancefloor than a muddy running track, but when all her friends were moving away and having children she joined a running club to make new friends. It was a steep learning curve, but just two years later she'd qualified in her age group for a World Championship triathlon and competed for Great Britain. The journalist has now written a funny, relatable memoir on her challenges and triumphs in getting fit, This Girl Ran. In this extract from the book she describes the first time she dared to take part in a 10 mile group run…

When I arrived at the schoolhouse for the 7pm start, there were at least twenty other people, of all ages, chatting familiarly, in running gear. I didn’t have to pay for my first session. The club’s website invited new runners to try a few sessions before they committed to joining fees.

I felt out of place in my designer gym kit, which I’d bought far more for its potential to impress the sexy personal trainers than I had for its sweat-wicking potential. My top didn’t have sleeves, so I put on a fleece over the top. No one runs in a fleece, by the way. Not proper runners. A fleece is far too warm.

When I ran alone I would usually set out in a fleece and stop to tie it round my waist when I got hot. Little did I know that there would be no stopping on this run.

The runners were grouping together for the three different distances. The furthest I had ever run in my whole life was 10k (6 miles) – and that was only two weeks previously, of which feat I was immensely proud. Maybe it was this pride which made me optimistic enough to join the 10-mile group. Maybe it was because, having made the move to even turn up that night, I was determined to make it count. Or maybe I was just so desperate to be accepted that I wanted to be considered an experienced runner. Whatever, I set off enthusiastically on my suicide mission.

The pace felt easy at first. We ran down the canal towards Limehouse, which is exactly where I’d just come from. No matter. I wasn’t here for new scenic routes. I was here to spend time with people and to get out of my deathly silent flat.

At 3 miles, I still felt OK – that was a third of the way already. At 5 miles, we reached Tower Bridge – the turning point. I was hurting by then and I had to do exactly the same distance all over again!

The club has a rule during Thursday-night group runs that no one leaves anyone on their own. All routes go along the Regent’s Canal, which can be a scary place once darkness sets in. I didn’t want to be the newcomer holding everyone back so I was determined to keep up.

My hamstrings started to hurt and then the balls of my feet. They hurt more and more, until I became convinced I was doing irreparable damage. Sometimes I closed my eyes, trying to forget the pain in the backs of my legs. I’d managed to remove my fleece on the go and now I kept having to tighten the knot around my waist to stop it slipping down.

I can’t stop. I can’t hold them up, I kept telling myself. In 40 minutes, I’ll be in the bar, and it will all be over.

‘Anyone want to pick the pace up for the return leg?’ one of the girls suggested as we turned around at Tower Bridge.

I was filled with horror.

Luckily, a nice, middle-aged man called Dave, who kept telling me in exasperated tones how he could no longer run as fast as he used to, came to my rescue.

‘I’m happy to slow down,’ he said. Then he added, for the fourth time that night, ‘I can’t run as fast as I used to.’

We dropped back as the others pushed ahead. We continued for another 3 miles, taking it in turns to repeat how I’d never run anywhere near 10 miles before, and how he couldn’t run as fast as he used to.

At mile eight, I couldn’t go on. Every muscle in my legs and feet ached.

‘I’m going to walk now but I know the way back. You go ahead,’ I said.

Dave wasn’t having that. He slowed with me and encouraged me to go on. Not wanting to rebuff him, I plodded onwards, resigned to the fact that my hamstrings would now be damaged for life. I’d torn them – of that I was convinced.

We carried on with this agonising trot for another mile and a half and only then, when the clubhouse was in sight, did Dave let me walk. He jogged ahead as I limped back, too exhausted and shell-shocked to feel sorry for myself.

I was the last back to the clubhouse and there was no hot water left in the showers. I went into the changing rooms sheepishly, listening to girls chat familiarly. There was a hairdryer on the side. I longed to feel it warm the crown of my head but thought better of it. I was among hardy, outdoorsy types now, and I didn’t want to be the prima donna preening herself. No one, I noticed, bothered with make-up, but I sneaked a touch of mascara on to my lashes while I thought no one was looking.

When I reached the bar, I paid close attention to people’s sartorial choices. This, I reasoned, must be ‘après sports wear’ – hoodies and loose jeans or comfortable tracksuits. As for me, I was in skinny jeans and a trendy knit from H&M. That was as close to casual as I got. When I’d packed my bag earlier, I’d changed my mind at least three times about what to wear in the bar. For me, it was more challenging to find a casual outfit than to piece together perfectly matched couture.

Much of my wardrobe was dry-clean only. My version of ‘dress down’ meant getting one more wear out of last year’s fashion before it went into the charity-shop bag. Aside from my running trainers and ballet pumps for walking to the Tube, I didn’t own any flat shoes. I owned every imaginable colour of shoe, handbag and matching accessory you can imagine, but I’d never owned a hoodie and I certainly didn’t own any thermals – that’s what black cabs are for!

Despite my greenness, I was determined to get involved. I saw this as a way out of the great empty void my life seemed to be floating in. On that very first evening, after that nausea- inducing 10-mile run, I set about finding out when and where the next club race would be. I didn’t care what it was, I wanted to do it. I didn’t have any competitive leaning. To me it would just be a new type of day out. A day out with new people; stimulation to take my mind off the break-up and my friends disappearing. A day out doing something new – something out of my city comfort zone. As it happened, the next race was on Saturday: two days’ time. ‘What,’ I asked someone at random, ‘do I need to do so that I can take part?’

This Girl Ran: Tales of a Party Girl Turned Triathlete (Summersdale), £9.99, is available on  Amazon