Standing amongst the thousands of other runners at the Blackheath start line, you feel that you are truly part of something immense.
Chris Brasher, co-founder of the race, called it: "The great suburban Everest - a peak for all to aspire to, but that relatively few dare to tackle."
But what is it that makes the London Marathon so special?
I believe the answer lies in the overwhelming support that the London crowd provides along every mile of the course.
In a city that can be notoriously alienating, it is just fantastic to watch as whole communities rally behind each runner out on the course.
There was a real sense of collective London pride, pride in the individual triumphs of the runners, and pride in our city.
The start was incredibly exciting, the adventure was beginning, although with the sheer volume of runners it took more than 10 mins to run across the start line after the gun was fired.
I experienced knee pain in those first few miles so I kept the pace slow in the hope that it would just go away, which thankfully it did!
By the time I was heading over Tower Bridge and towards the halfway point, I was running comfortably.
Family and friends were along Westferry Road at 16 miles to cheer me on, and this spurred me towards Canary Wharf, a part of the course traditionally known as the most difficult.
Many runners experience the dreaded wall around 18 miles. Happily this didn't happen to me. Crowds packed the streets and, having plugged into some Britney Spears music on my ipod, I was simply loving the experience.
I definitely picked up speed at this point, probably because I had run slower than normal over the first half.
The only frustrating point was the huge queues at the toilets that took up at least 20 minutes, but it was a chance to stretch and chat to other runners.
Heading down the Victoria Embankment the heavens opened, but nothing could have dampened spirits on that day.
I couldn't believe it, I was at mile 24, and if I kept pushing it I would finish in under five hours, which was my target time.
I put aching limbs out of mind. I was going to finish this beast and finish well! I gave it everything I had over that finish line - I did it!
Four hours 52 minutes 19 seconds was my official time. I could not have been happier if you had offered me the whole world in that instant.
I ran for Great Ormond Street Hospital, I ran to see what I was made of. I faced this crazy mental and physical battle and won.
I would like to thank my family and friends who supported me all through training and on the day itself. I would also like to thank Dan Brockhurst, my trainer, who helped me to realise a life's ambition.
Don't just consider running a marathon, do it, it will change how you see life.
As Czech athlete Emil Zatopek said: "If you want to run, run a mile. If you want to experience a different life, run a marathon."
You can also visit the Five Live messageboards to chat with other runners about your marathon experiences.
