There are no stairs or escalators to take you up to Terminal 4 from the underground Heathrow Express platform. Beyond the ticket barriers are four lifts, summoned by a single button. As lift buttons go it’s a big one, about three inches square. As I advanced, finger outstretched, I thought of the tens of thousands of forefingers from all over the world that have pressed that button since people started dying in China from what my Sun newspaper graphically calls ‘snake flu’.