I beat Amanda Holden!

It might seem obvious, but I can officially confirm that running a marathon is the hardest thing I have ever done in my life.

I've woken up this morning with aches and pains in muscles I didn't even know I had. And I haven't tried walking down any stairs yet, but I can guarantee I won't be facing forwards when I do.

But I've done it and I did it without walking - albeit at a speed somewhere between that of a snail and a sloth for the last six miles!

I even managed some semblace of a sprint finish - there's nothing like an announcement telling you Amanda Holden is near the finish line to spur you on!

And I don't think I'll take my medal off for two weeks - such is the sense of achievement.

It all started when I got on the tube at Stratford yesterday morning. It was like a sardine tin of runners, all cheek to cheek, my gold helium balloon getting in everyone's faces and on everyone's nerves.

But amidst the crowds, I spotted a familiar face, or to be more accurate, a familar pair of socks. A girl wearing a bumblebee outfit with these excllent yellow and black socks that I'd coveted at the Belvoir half marathon three weeks ago.

Next thing, I was chatting to her and her mum (dressed as a ladybird incidentally) and they became my inspiration. That's how it went all day. Every other runner is an inspiration and helps you get round the next corner.

Standing at the start line with my running partner, Emily, it was all just a bit surreal. This thing that had consumed our lives for the last four months had finally arrived and it didn't feel real somehow.

Despite all the people, it just felt a bit like another training run. It wasn't until we crossed the start line, squealing like children, that it hit us. And we were off.

Usually, running together, it's a chance for us to chat, to catch up on all the gossip. But we have never been so quiet as we were running the London Marathon.

It was a combination of nerves and excitement, and there was just so much to look at. We couldn't speak because we were too busy people-watching - trying to spot any familiar faces in the crowd.

The first five miles were fairly uneventful. Other than my shoelace coming undone and ever other runner tapping me on the shoulder to tell me so, running was easy with all those people.

We knew we were being pulled along a bit too fast for us but we didn't care. We were just enjoying it. At five miles, we first saw the TV cameras and waved furiously at them, closely followed by my history teacher, Mr Bott, in the crowd.

I hollered at him (later discovering he was there to watch his wife run) but he didn't hear me.

Next, we passed the Masai warriors. This group of six Tanzanians had flown over to Enland to raise money for their village. Dressed in rubber shoes and carrying spears, they were a fantastic spectacle.

No end of superheroes, near-naked men and Pink Panthers followed, but the warriors were definitely the highlight.

Our first major milestone was 11 miles, where we knew Emily's boyfriend would be standing.

He was there, along with loads of Em's friends, dressed in green T-shirts supporting her charity, FSID, and in spite of the now torrential rain, it gave us a big boost.

At 13 miles, we'd reached halfway and, still feeling pretty good, we spotted my boyfriend, Andy, on the top of a double decker bus. That really helped me for another few miles.

Mile 14-17, heading out to the Isle of Dogs is slightly no-man's land. Few supporters and I was starting to flag. But then bumblebee and her mum passed and gave us a bit of a boost. It was just a quick chat, but it's these little things that keep you going.

At 20 miles, we saw Em's boyfriend Simon and her friends again. By this point, she was stepping it up and I was heading down a dark tunnel of despair. I managed to perk up slightly to see Andy again, along with my sister and brother and his little girls at 22.

But from there on all I could think was, 'I want to walk, I want to walk, I want to walk'. Funny that, when it's the last thing I want to do this morning!

We knew that if we really pushed it, we might just about make four hours, but I just didn't have it in me to push it. I was seriously flagging and it was all I could do to just keep going.

The crowds were great, and although my gold balloon was somewhat deflated and hanging halfway down my back at this point, I still got a few cries of "Go Jax" to keep me going.

But even at 25 miles, when I knew there was just a mile left, I still wanted to walk. I REALLY wanted to walk.

And as I spotted the time - 3 hours 58 minutes and 45 seconds, I began cursing my boss, Fletch, who had told me time and time again that I would do it in 4 hours. I knew I wouldn't now and it was making me feel like a failure.

At 600 metres I knew I could do it. Though by now I was cursing the stupid person who decided the marathon had to be an extra 385 yards over 26 miles.

And then I heard the announcer: "Here's Paddington Bear, crossing the finish line now," he shouted. ('I've been beaten by Paddington Bear?' I thought, faintly horrified.)

"And now let's all look out for Amanda Holden," he continued. "I've heard she's not far behind." Right, I'm not having that. With every ounce of energy I had left, I broke into a sprint.

OK, maybe not a sprint but I was certainly going as fast as I could muster. And I crossed the line, with Emily right beside me, in a hailstorm. Four hours, nine minutes and 51 seconds.

We'd done it. If it wasn't for the hailstorm and the pain in my legs I would have been over the moon. What a flipping achievement!

At 15 miles I'd sworn I'd never I'd it again. But as soon as we finished, Em gave me a card, thanking me for supporting her and inviting me to join her in New York 2010. Well I have to beat that four hour mark don't I?!