The Davies Commission acknowledged that a second runway at Gatwick would have far less impact than a third at Heathrow / AFP/Getty

Gatwick plans to press ahead with a second runway regardless of the outcome of the Government’s decision over airport expansion in the South-east. Simon Calder explains the obstacles ahead

Legally, feasibly can Gatwick do this?

Yes. Assuming the Government gives Heathrow the go-ahead, Gatwick could in theory simply apply to West Sussex County Council for planning permission to build a second runway. Much of the land for the airport’s preferred site, south of the existing runway, has already been reserved for possible expansion. But it is more likely that Gatwick’s owners would seek support from the National Infrastructure Commission, which is charged with creating “effective and efficient infrastructure for the UK”.

Who pays?

Not the taxpayer, according to Gatwick. Airlines believe the airport’s owners should fund the project, likely to cost around £8bn, and then collect revenue from the increased number of passengers. But whichever runway project goes ahead, it is likely that airport charges will rise during construction.

What about the environmental objections?

While there is a vocal lobby against expansion around Gatwick, and more widely against the increase in aviation, there is nothing like the antipathy that exists towards Heathrow. The Davies Commission acknowledged that a second runway at Gatwick would have far less impact than a third at Heathrow.

If Gatwick goes ahead regardless, what was the point in the Davies Commission and the subsequent government decision?

Cynics maintain that the Davies Commission was simply a political manoeuvre by the 2010-15 coalition government to kick the runway issue into the long grass. But Sir Howard Davies and his team carried out exhaustive research on the possible options and narrowed the Government’s choice to just three options: Heathrow’s “official” plan for a third runway; the “Heathrow Hub” plan to extend the northern runway; and a second runway at Gatwick. It also ruled out Boris Johnson’s preferred scheme for a new airport in the Thames Estuary.

It is still possible that the Government may give the go-ahead to both Heathrow and Gatwick. In any event, it would be politically difficult for Theresa May to overrule a private-sector initiative for a major infrastructure project requiring no public funds.

Could Heathrow sue?

Bosses at Heathrow are confident they will get the go-ahead to expand, and will be exasperated if Gatwick’s intervention protracts the planning process. But more likely they will express public indifference to their rival’s plans, knowing that passenger demand at Heathrow is much higher, and its slots are accordingly far more valuable than those at Gatwick. A single pair of take-off and landing slots at Heathrow are rumoured to have recently changed hands for £65m.