In the mid-90’s I was commissioned by the Guardian to write a series of reviews of books about cities. The first, on a book called “The Pig and the Skyscraper” gave me the chance to write about Chicago from where I had just returned (and which remains for me the most truly American of cities).Two more general books, one by John Reader and one co-authored by Philip Dodd and Ben Donald, broadened the portrait. California came courtesy of Kevin Starr. The article on burning libraries was commissioned by the Gøteborgs Posten and one on the Thames by Profil magazine. The piece on London bus numbers was really a collaboration. My children started it off with conversations at bus-stops. The novelist Ingo Schulze and Georg Boomgaarden, the German Ambassador to the UK (and a keen bus-user) followed up.