Charity Crewe never imagined she'd run the London Marathon, but it's amazing what a couple of glasses of wine can make you do...

My first experience of the London Marathon was as a spectator waiting on the finish line for my friend Tracy. For about 10 minutes I was amused by the assortment of costumes ranging from rhinos to gorillas and even a Charles II; amazed by a sprightly jogger in her 70s and a man with one leg breeze past able-bodied runners.

But after an hour of waiting in the freezing cold, watching the pained expressions on the runners' faces, and having clearly missed my friend, I couldn't be more sure this was something I would never do myself. A certainty that was further confirmed when Tracy told me that she'd been sick in a bag at the end of the 26 miles and couldn't walk for the next two days. Why, only two years later, I decided to take up the challenge of the Marathon is largely due to a drunken agreement at a party.

There is nothing like a good cause to get people doing things they wouldn't have previously considered; whether it be forking out hundreds for a submarine ride at a charity auction or agreeing to sit in stocks to be pelted with mouldy fruit at a summer fair.

I deputy chair the Q Trust, a fundraising venture set up in the name of my late father, Quentin Crewe, to raise money for Muscular Dystrophy, a muscle-wasting disease he suffered from all his life. So when, at a party, Malcolm, a family friend, said he was running the Marathon for the Q Trust and suggested I joined him, I couldn't really refuse. When I tried insisting I hadn't ever run - except to catch a bus - he pointed out that there were still several months to go before the race. So, with a belly full of wine, I slurred: 'Ssyesh, ok, schvery good idea.'

I didn't give it much thought until after the Christmas break, when I returned to a flurry of emails from Malcolm, saying the deadline for signing up was looming and I had to sign-up straightaway. By the time I'd signed my agreement form, it was well into January and the April 13 race day was breathing uncomfortably down my neck.

My decision to run the marathon was met with surprised approval from friends, followed by a series of second-hand horror stories of toe nails falling off, bleeding nipples, unexpected bowel movements and even permanently damaged knees.

The benefit of hearing stories of doom was that I resolved to splash out on the right kit. I went to a running shop called Run and Become in London. Here they make you jog down the street to see what peculiar running habits you might have and fit you out in the right pair of running shoes - always hideous, nearly always white.

The actual training was more of a challenge. I did have an advantage over the average couch potato, because I have always cycled to work. But I'd never jogged in my life. I also hate getting up early in the morning and I didn't fancy jogging in the dark after work. My friend Stephen came to the rescue by appointing himself my coach for a month. He would buzz on my door and make sure I got up. He would then cycle along as I jogged.

Although Stephen knew even less about jogging than me, he was a fairly strict coach and wouldn't let me stop for a breather until I'd done at least a couple of miles. The extraordinary thing about jogging is how quickly one builds up stamina. After a couple of weeks, a half-hour run wasn't so difficult.

Most people suggest that you start training in November, but it was obviously too late for this. I usually managed two one-hour runs a week and a couple of times did three. I meant to give up drinking for a month before hand, but that lasted all of a week. I didn't manage to quit smoking either.

My fund-raising efforts were much more successful, thanks too the wonderful website Just Giving. If your charity has teamed up with the site, you can create your own marathon web page, email the address to your friends and they can then sponsor you online, using a credit card. By April 13, I had been pledged £1,500, which gave me a huge incentive to finish the race.

The big race
The marathon starts in Greenwich at 9.30am. My biggest fear was oversleeping, so I stayed with Malcolm the night before. By the time we reached the starting point in Greenwich Park, I was feeling a flutter of excitement. Due to the number of people taking part (33,000), it takes about 12 minutes to cross the start line. An electronic tag inserted in your shoe registers your take-off. There are secret check points throughout the race that keep track of your tag and ensure you've actually completed the course, rather than cheated by jumping on the tube.

The organisation of the event is phenomenal, every mile there are water points and every four miles, energy drinks. The crowds are what really keep you going though. Kids wait with a hand out to touch you or give you sweets. When I was feeling bored, grabbing as many jelly babies as possible kept me amused. The other bonus of the crowd is that you sense their disapproval when you start walking. Indeed they tend not to call out your name, which most people write on their t-shirts, if you're not running. Not that many people called out for me - with a name like Charity, there was bound to be some confusion.

After 11 miles of jogging with Malcolm, I decided I needed a bit of a walk. Left to my own devises, I adopted a walk-run policy. When I found myself being overtaken by a centipede propelled by six pairs of hairy legs, I decided it was time to run again. And when I got stuck with Elvis, who was hogging all the limelight, I shot off again.

By mile 15, my legs were in pretty bad shape, so when I spotted some runners being massaged on the side of the road, I thought I'd get in on the action. It turned out to be a neuronetic massage devised by Ron L Hubbard (sci-fi author and founder of the Church of Scientology) and the very friendly lady attending to my weakened limbs was a Scientologist. Slightly freaked out, but rather enjoying the 10-minute lie down, I listened eagerly to the wonders of Dianetics. I gave my old address to a man with a clipboard and ran off.

Passing the London Arena at mile 17 was a bad moment. I had been there a few days previously to register for the Marathon and it had taken a good 40 minutes by tube. At mile 20 I passed the Tower of London and realised I was actually going to finish, if not in the four and a half hours I had optimistically predicted.

When Big Ben appeared round the bend in the Thames, a wave of adrenalin kicked in. Here the crowds were solid and particularly vocal. I had a corny image of myself running in slow motion in Chariots of Fire as I pelted it round Parliament Square and up Birdcage Walk. I spotted Tracy waving from outside Buckingham Palace and then ran through an arch of balloons to collect my medal. I made it in 5hours 35minutes. Paula Radcliffe won't be quaking in her trainers, but I was quite pleased. Not one single blister, no bleeding nipples and only a vague stiffness the next day.

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