Seoul for the C40 Summit

It's a long way to travel for a climate conference. My flight - as always - was offset. I'm travelling with just two of my aides, booking economy flights and seeking the best value for the taxpayer at every stage.

Nevertheless I feel a need to justify this trip. I hope the other Mayors signed up to the C40 group share that.

We cannot cross the globe to exchange platitudes and sign bland documents. Sharing best practice is valuable, passing on tips and subjecting each other to peer pressure on the vital challenge we all face of combating climate change is obviously useful. As Deputy Chair of this Group, and with London hosting the C40 Secretariat (though another city picks up that bill) I'm more than happy to be here. But if this summit is worth holding, it has to prompt practical and noticeable change. Colleagues will have their own ideas. I will propose my own at dinner tomorrow.

What I read on a long flight, and what i witnessed of South Korea from the airport is impressive. The 13th largest economy in the world has slowed down like everyone else, but it's still growing convincingly and the roads, rails, bridges and building into town are proof of the enormous infrastructure improvements that have gone along with that. But they're also on a mission to improve the feel of the city - much as I aim to do in London. A haggard old highway in the city centre has been cleared, an old waterway rediscovered and set in a striking urban park.

There are large clusters of trees as well as sky scrapers defining the view from my hotel window, and my jog, just now, took me through some beautiful landscape. I hear good things too about the site of Seoul's Olympics two decades ago and look forward to visiting that tomorrow. There are always lessons to be learned, and this seems a good place to study.