Although by this time I had taken part in the Moonwalk and knew I had the stamina and sheer determination to cover the miles, it was still very daunting.
Luckily my pal Joyce agreed to do the race with me and we started training in the freezing cold of the New Year. We had the help of fitness expert Jane Wake who gave us a training programme that was tough but achievable.
You really do have to put in the hours and the miles and there are no short cuts.
Joyce and I started off slowly and built up the pace and the distance, but it was really hard.
The night before the race, I didn't sleep a wink because of sheer nerves.
Starting at the front of the crowds waiting for the starting gun was terrifying, especially when everyone elbowed us out of the way in order to get a quick getaway.
It was hard to resist the temptation of going off like a two bob rocket, but Jane had warned us to pace ourselves and not use up all our energy in the first part of the route. So many people make that mistake and they are the ones you see falling by the wayside or crossing the line looking like rubber men and women with jelly legs and wobbly heads.
It was an amazing day and the crowds really helped by cheering us on and giving us sweets and ice lollies.
I have never been so exhausted or so glad to see a finish line. Rosie was there to give me a cuddle, but Joyce and I didn't cross the line together as planned.
She had spotted a clutch of photographers and raced ahead because the drizzle had made her hair go all curly!
Although I was beaten by a couple of Cornish pasties and a 94 year old man, I was still proud of myself for finishing.
Going into work the next day was agony. I had to do a bum shuffle to get down the stairs and walked as if my legs were pinned to my shirt.
I vowed that never, ever again would I put myself through such pain and torture.
So where did you find me exactly one year later?
You guessed it. I was at the starting line again. This time with Joyce, my husband Steve and my pal Craig Millar and we were all preparing to do the London Marathon once more.
I was suffering badly from a cold, and a doctor reluctantly agreed that I could go ahead with the race, but wanted to keep an eye on me. You really shouldn't run a marathon if you have a temperature, but I was borderline and given the benefit of the doubt.
I found the 2005 race much tougher than the first time.
I knew the course and was all too well aware of just how hard it would be and I hadn't trained nearly as much as I should have.
Once again the crowds were fantastic, cheering us on and I just had to keep focused on the money we were raising for charity.
I honestly don't know how I managed to complete the course, and by the last six miles I was running on empty and felt horrendous.
Sheer determination (what we call being thrawn in Scotland) kept me going. My time was slower than the first, but I was just glad to have made it across the line again.
So you would think that I would have had enough of marathons. But no.
Later that same year I called Joyce to ask her if she fancied a weekend in New York. She said yes before I told her that it wouldn't be a few days of buying shoes and drinking Cosmopolitans like the girls in sex and the City, but that in fact we had a chance to take part in the New York Marathon.
Highland Spring was sponsoring runners and they also were going to double any money we raised for breakthrough Breast Cancer.
How could we possibly refuse? The team posed for pictures in Time Square the day before the race and Joyce and I had a Bloody Mary each the night before, convincing ourselves that the tomato juice was full of iron and therefore would do us good.
Despite being an incredibly tough course, I found the New York marathon easier than London. I don't know if it was the sheer excitement of being in Manhattan, the time difference or the fact that there were so many New York fire-fighters shouting encouragement, but it wasn't quite as exhausting as the other two races I took part in.
It also helped that my pal Siobhan flew from Belfast to New York to cheer us on. She and her friends kept driving ahead of us and waving a Scottish flag as we passed. It really lifted our spirits.
Although it was November, New York was incredibly hot and people were drooping in the sweltering humidity. I ran with an icepack down my boobs for about five miles until it melted. I felt so sorry for a group of British squaddies who were running in full uniform and carrying heavy backpacks, but the New Yorkers gave them a tremendous ovation.
The race finished in Central Park and Joyce and I managed to limp back to our hotel and have a couple of hours rest. I couldn't go to bed, because I had to stay up until midnight to go into the GMTV studio in Times Square to do a live link into the programme.
I don't think I made any sense at all during that appearance, as I was beginning to feel completely woolly headed. After the show was over, we jumped into a cab and headed straight for airport to catch an early morning flight as I was on air the next day.
It was an incredible experience but I promised myself I would never do it again. My feet were like a couple of pounds of raw mince, my toenails were black and eventually fell off and I was walking like a 100 year old woman.
Of course you should never say never and this year Steve and I and Joyce and her fiancé Paul will be at the London starting line for my VERY LAST marathon.