Do you remember the first time?

Yesterday I picked up my number and my tag for the 2012 London Marathon. It's official - I'm doing this thing.

This will be my third marathon in 30 months. No big deal, given some of the awe-inspiring marathon charity challenges that take place each year. But as I get ready for this third time out, I can't quite believe how that first-time feeling won't go away.

I started big - with the 40th running of the New York Marathon in 2009. I trained dutifully, petrified at the challenge I'd set myself. The training went fairly smoothly, no major hiccups. My aim was to get round in a time that would get my name listed in the New York Times the next day and to enjoy running in a city that I love.

Like all American things, it was big. The whole thing, not just the race. The expo, the goody bag, the pre-race preamble. But most impressive of all is the way the city embraces the event. There are points on the course where it seems like the whole of New York City is stood at the side, shouting your name. There are points where there are few spectators but they usually make up for their number with a great chant. The lone fat lady in Harlem who shouted 'Go Anne Marie, that's what I'm talking about' has gone down in folklore for my family and friends.

My second marathon was Berlin. Again, the training went well. I tried a different plan, with a lot more mileage in it. I was aiming for a sub 4 hours 20 time, and a great experience in another city I love. Berlin is also big. It is tall, in its own Northern European way. It also generates a city-wide atmosphere, but not to the same extent as New York. There is great support (particularly if you are Danish), the organisation and route is faultless, and you can even get a massage en route, but it wasn't quite the same experience as New York. I did, however, beat my New York time by almost 15 minutes, so it was a fantastic marathon for me and has a special place in my heart. The final stretch down the Unter den Linden was incredibly emotional and gives you fresh legs to hit the finish line strong.

And now's I'm getting ready for my third marathon. In the city I love most of all, the city I call home. The city that can still make burst with pride to live here, and make me want to slap it for being so stupid. The training has gone ok, with more hiccups than previous years. But I feel fit and ready to run. I'm excited to run it, and intrigued to find out whether being able to eat my own food and stay in my own bed in the days beforehand will have  a positive impact on my performance and time.

But I'm more nervous than ever. The nerves don't go away, no matter how many you do. So much can depend on the day. What will the weather be like and how will that affect me? What will the crowd be like? Can it emulate the New York support, or will it be more sporadic, like Berlin? What will my stomach do? Will I need to stop for the loo, adding precious minutes to my time? How will I feel running without my marathon buddy from New York and Berlin? Will this make a difference to me at the start?

But most of all, will London do something to make me love it like I love New York and Berlin? What reason will it give me to make it special for me?

The nerves, the anticipation, the wonder - these are all part of the buzz of the marathon. The gift that keeps on giving.