Why does Sheikh Mansour own Manchester City? Because it is a good business. It’s a prestige purchase that gives him exposure. You could say that the Roman Colosseum is a living, breathing thing, more than just a millennia-old monument. But in its own time, it was the Etihad Stadium par excellence. Diego della Valle, a Berlusconi-type figure yet with unimpeachable ethics, has chosen to enliven the smog-dusky outer layer of the amphitheatre, cleansing the pores of its travertine stone, with a three-year facial.