Andrew Marr looks at transport routes and finds out how the world's megacities stay fed, and he joins Mexico City's traffic cops in the air.

Andrew Marr takes a look at safety and security, two of the biggest challenges faced by each and every metropolis, visiting Tokyo, London and Mexico City.

Documentary in which Andrew Marr looks at how people live in five of the world's biggest megacities: London, Dhaka, Tokyo, Mexico City and Shanghai.