Can you explain the sense in which the taxpayer will be underwriting the £18bn. HAL is a regulated utility, the £18bn will be recovered through aero charges, see the PWC report on the AC website which Basil Bush and others have referred to previously. Do you really think there's a risk the traffic won't stand it and HAL will go under?
The £6bn for the M25 tunnels and the station is an assumption. Govt has not said that's what will happen if R3 gets the green light. That is all to play for.