Agonising about new airport capacity in southern Britain has been going on since 1971. Should an extra runway be built at Heathrow, London’s biggest airport, or Gatwick, the second-biggest? London needs more capacity: last year its three main airports (Heathrow, Gatwick and Stansted), with four runways between them, handled 130m passengers, 10m more than New York’s main three, which have nine. No new full-length runway has been built near London since the second world war. Meanwhile China has built 80 airports since 2012 and last year Dubai overtook Heathrow to become the world’s busiest international hub. Today, after three years’ rumination, Sir Howard Davies, an economist, has issued a report recommending the expansion of Heathrow. Businesses will be pleased; but Boris Johnson, London’s bumptious mayor, opposes the plan and has threatened to lie down in front of the bulldozers. Sir Howard has made his decision. Now the government must act on it.