The bosses of some of the world’s biggest airlines received a strange request last year from Heathrow airport — it wanted to spend £74,000 to chop down three trees. A little research suggested that the quoted price was up to 20 times what a tree surgeon would normally charge for the simple task, if the trees were located elsewhere. Yet this type of scenario has become commonplace at Europe’s biggest airport, carriers claim.

Under a complex — and some say perverse — incentive system, the west London hub is encouraged to spend as much as it can on developing the site. Heathrow’s investors earn a return based on the size of its regulatory asset base (RAB), under a formula set by the Civil Aviation Authority