In this extract from her new book, (written with Ian O'Riordan, Irish Times sports journalist), Catherina McKiernan explains how she won the London Marathon

If there was one race in my whole career where I went to the starting line knowing I would win, it was the London marathon in 1998. My mindset going into that race was the perfect blend of self-confidence and determination. The training had gone superbly well, so I knew it was going to take someone very, very special to beat me. I hadn't lost a race in almost a year. And the fact that I'd missed the World Cross Country to concentrate solely on my preparations for London completed my determination to win.

The race was set for Sunday, April 26th, and the organisers wanted me over for a press conference on the Thursday before. That would have meant three nights in the hotel before the race, and I wanted to stay in my own environment for as long as possible. So we agreed to go over on the Tuesday to do the press conference, come back that evening, and then head back over for the race on the Saturday, just 24 hours before the start. This was Joe (Doonan, coach) at his meticulous best once again.

My last hard training session was set for the Sunday before, when I did a one-hour threshold run out on the Dublin-Cavan road. By threshold I mean running close to my maximum, in this case just under marathon pace. Joe wanted to make sure everything was right and arranged to take blood samples as I was running, to measure the lactate level.

Bernard Donne from Trinity College came up to Cavan for the session and brought a little device to measure the lactate while I was running. He would drive up alongside me at intervals and I would prick my finger on a blade extended out the window of the car. The tiny blood sample was then analysed by the computer. It essentially gave a read-out of how well my body was coping with the stress of fast-paced running. From the results I knew it was coping very well. That's how thorough the preparation was.

I thought I was well used to seeing big hotels, but the Thistle Tower, where they set up the headquarters for the London marathon, was particularly impressive. I sat through various radio and TV interviews before the main press conference. I know I'm every journalist's' worst nightmare, but that's just the way I am. I don't like being in the spotlight and worse still the centre of attention at a press conference.

I tried to give the English journalists some decent stories about playing camogie in school, and Pat Spillane being my hero, but no one seemed to get that. Paul Kimmage was one of the Irish journalists present, and he came up afterwards asking for another interview. I didn't know him at the time, but I thought we'd had the press conference over with, the questions went around to everyone, and he sat at the back and didn't open his mouth.

It irritated me that he did not ask a single question during the main press conference. He could even have asked something that might have interested the other journalists and helped them get more information out of me. Anyway, I just said, 'well, you had your chance'. I wasn't trying to be smart. I didn't know who he was. But I'm sure I sounded a bit cheeky. So he went off and did a piece with Joe later that week instead.

I didn't actually mind too much talking to journalists as long as someone caught me straight after a race. I'd be on a high then. But an hour or so later I'd be gone back into my shell, and it would be a lot harder to talk. The only time I read anything about myself was when a paper was handed to me on a plane coming home from somewhere. I would buy them after a race sometimes just to see the pictures of myself, but I never enjoyed reading about myself.

Damien (O'Reilly, husband), Ray Flynn (agent) and I left Dublin early on the Saturday morning and flew to London. From the moment I stepped off the plane it was royal treatment once again. First port of call was the BBC television studios, where Brendan Foster did a 10-minute interview with me. Damien was there too and was in his element being in the same studio as Gary Lineker and Trevor Brooking, who were doing Football Focus just a few feet away. Damien grew up watching Football Focus on BBC and I don't think he could quite believe he was now watching it live on the actual set.

Suddenly, it was one o'clock and I was on the verge of starvation, the last thing you want to be the day before a marathon. Ray Flynn mentioned this to Brendan Foster and he recommended a restaurant close to the BBC studios. That will do nicely, I thought, and as usual asked for a plate of plain pasta. Not for the first time, my order met with a strange look from the waiter, and when the plate arrived it came with some kind of sauce on it. Not wanting to offend Brendan, and obviously in need of food as soon as possible, I cleaned the plate. I remember thinking at the time that the sauce tasted like it came out of a packet, but I didn't give it another thought for the rest of the day.

I never had much problem getting a good night's sleep before a major race, and the London marathon was no different. Except I had to set the alarm for 5.30am, exactly four hours before the start, to give myself time for breakfast. As usual that meant a few slices of the trusted brown bread, a banana and a glass of a carbohydrate drink. I lay down for another half hour or so and then headed down to the hotel lobby to get the 7.30am shuttle bus out to the start.

While waiting for the bus I got to see my main rivals for the first time. Joyce Chepchumba of Kenya was one of the other favourites and got to wear number 101, which traditionally goes to the defending champion. I was wearing number 102. Liz McColgan of Scotland was another former winner and was still one of the toughest runners around. Marleen Renders of Belgium had recently won the Rotterdam marathon and was there too, as was Marian Sutton, who had won the Chicago marathon twice. Each of them probably believed they would win just as much as I believed I would.

I met Ray in the lobby and he seemed a lot more on edge than I was. Joe had arranged to get out to the start with me and then follow the race in one of the lead trucks. The London marathon was one of the few races I remember watching on television as a youngster, but I never once dreamed about winning. This didn't feel like a date with destiny or my chance to become one of the marathon greats of our time. It was really just another race for me.

As usual for a big city marathon, the organisers had brought in a few pacemakers to ensure a fast time. But they went out a little too quick and I was in no rush to go with them, and neither were McColgan and Chepchumba. Two runners that did get away were Mexico's Adriana Fernandez and Romania's Lidia Simon, both very capable of winning. For a good while, though, I was happy to run with the main group, thinking those up ahead were going too fast to hold on.

Then at around 15 miles I started to feel a rumbling in my stomach. Our pace was a little slower than planned early on and at first it felt like the carbohydrate drinks were building up in my stomach because of that. Then I started thinking about that pasta sauce I'd eaten the day before. Oh no, what could it be? Something in there wasn't agreeing with me.

For the next mile the cramping got steadily worse. I realised I had two choices: I could pull over to the side of the road and pray I might find a toilet or I could just keep going and pray nature wouldn't take its course. Before I had a chance to make up my mind, nature made it up for me. Embarrassing as it was, there wasn't one moment when I considered stopping. At that stage I was just hoping the television cameras would stay in front of me and not get any close-ups from behind. I just cursed the pasta sauce for a couple of minutes and strode on.

I'd had a few minor problems with my stomach on long runs before, but nothing like this. But it's part of marathon racing. I heard afterwards that Steve Jones had a similar problem when winning London in 1985. And we saw it again in the 2005 London marathon when Paula Radcliffe had to make a brief stop to answer the call of nature.

I cursed that pasta sauce one more time. But there was only a small moment of panic. Once nature had unkindly taken its course the cramps more or less disappeared. More importantly, the legs still felt fine.

At 16 miles word came back that the two leaders were 95 seconds ahead. That's a considerable lead with just 10 miles to run. And it was then that Liz started telling me I'd better go after them if I wanted to catch them. She was struggling with the pace and apparently having stomach problems of her own.

So I took her advice and started the chase - and within the next mile or so I could see Fernandez and Simon just a few hundred yards up the road. Sixty seconds became 40 seconds and then 20 seconds. I dropped one of the fastest miles of the race, 5:15, and that brought me right up to them at mile 21.

I took a quiet glance at Fernandez and could tell straight away she was finished. Within a few more strides I was gone past them both and all I had to do then was hold on. I was bouncing off the road just like another training run. I could hear the shouts for Liz McColgan back the road, but there was no way she was going to have the speed to catch me.

There is no better feeling in running than coming into the final miles of a major marathon knowing you are going to win. I got that feeling in Berlin and was having it again in London. With about two miles to go Joe suddenly jumped out from the side of the road and ran along with me for a stride or two. Lets go, he shouted. He'd obviously seen enough from the lead truck, and this was his way of saying I'd won, now finish it off in style. I had my own theory about the last miles of a marathon. The quicker I run, the sooner I'll be finished. So I ran those last two miles as fast as I could.

As the crowds thickened even more and I turned into the famous final stretch down The Mall my first feeling was relief. Just like it was when I'd run well in the World Cross Country. I had got to the stage where winning was a formality. I was at my peak, 28 years old and in the prime of my health. I'd fully expected to win and was just relieved that I did.

As usual I glanced up at the clock coming through the finish - 2:26:26. Nothing wrong with that, I thought, considering the obstacle I'd met along the way. Most of my family, including my mother and father, had travelled over and I could hear them shouting at me from the VIP stand. I was more concerned about concealing the embarrassing aftermath of the stomach cramps. I asked one of the finishing officials to get me a towel and get it quick.

Then I was handed one of the large foil sheets they give you to keep you warm, but instead of throwing it over my shoulders I quickly wrapped it around my waist. Now I could go about waving to the crowd.

For the rest of that day I was on an absolute high. The winner's prize was $55,000, plus the usual bonuses, but to me that was just more money in the bank. I would have got just as much satisfaction out of winning London if there wasn't a penny in prize money. Winning was all I cared about.

About a half an hour after finishing I was handed a mobile phone. President Mary McAleese was at the other end of the line to congratulate me. Her husband, Martin, whom I got to know through running, also had a few words of congratulation. It was very thoughtful of them to call and made the occasion ever more special.

I also met Sonia later that evening when she dropped into the Thistle Tower. She'd followed the whole race from the press room. She said well done, and I congratulated her on her wins in the World Cross Country, the event I'd sacrificed to win the London marathon.

By the end of the day it had begun to sink in that I'd won something big. The London marathon was an event the whole family used to watch on a Sunday morning after Mass.

Now they were all there to see me win it, except for Seán, who had to stay home and mind the farm. Giving the family that thrill was one of the main reasons I was running these big races in the first place, and London was a particularly special moment.

So much of the satisfaction I got from winning was seeing other people, and in particular my family, enjoy the moment. I remember saying that to Joe once, that I just wanted to win for my family and neighbours. And he couldn't understand that. You're joking me, he said. But that was the truth.

London brought that satisfaction more than any other race. I remember hearing from my Aunt Annie Fleming, who lives in Nottingham, that people were congratulating her at Mass the following Sunday, people who hardly knew her. I got a great kick out of that. Back in Coronea, Fr McGoldrick said the 10 o'clock Mass in a record 20 minutes so everyone could get home to watch the race.

And in Killeshandra, Fr Hurley was apparently keeping people informed of my progress during 11 o'clock Mass. Shortly after Communion he announced that I'd won, and everyone broke into a round of applause, when they were supposed to be deep in prayer. I got a great kick out of that too. I also heard there were people sitting outside the church listening to the race on the radio.

I think I also realised in London that no matter how well I looked after myself, I wasn't going to have too many days like this. In a strange way I felt that winning it once was all I needed to do. At no stage in my career did I feel running was about winning titles. Winning London was never something I dreamt of. The profile meant nothing to me.

I loved the winning feeling, but no more than the feeling of preparing to win. And all through my career I never wanted to race unless I was properly prepared.

Over the years I've got to appreciate that victory in London more and more. In April of 2005 I was invited back for the 25th-anniversary race, where I got to meet almost all the former winners. I didn't fully appreciate it at the time, but being with all those former champions certainly made me realise how important it was to win London.

Many great runners have tried to win the London marathon and never did, and after a very enjoyable weekend celebrating the 25th anniversary I knew in my heart that the Past Winners club in London is a great club to be part of.

Still, as with most of my running career, the marathon was something I more or less drifted into. I wasn't fulfilling any major ambition by winning in London or anywhere else. It wasn't a personal mission.

If anything it had become more like a job at that stage. I just found myself in the situation where I had everything in place around me - sponsors, coaches, agents, everything like that. So I couldn't stop even if I wanted to. I will always appreciate my success in London.

I loved to run long before any of the success happened. The running brought me out of my shyness to a certain extent, but it brought on new burdens of its own. The more successful I got, the more trapped I felt - that I had to keep going now, try to win this or that, because I was on a roll now and, like anyone will tell you, you don't stop rolling the dice when luck is on your side.