As we swoop down over Mexico City a sprawl of lights twinkles like the end of a U2 concert.

The knots in my knees are second only to the knots in my stomach, and I can't speak a word in any language. So the taxi driver can rip us off all he likes.

Heading towards the Zocalo, we're overcome by the heat, the dust, the smell and the noise. We're not going to sleep much tonight.