PM explains why decision on Heathrow has been postponed for 6 months

Mr Humphries*, "Prime Minister, why have you delayed the decision on a third runway at Heathrow for another 6 months?"
Mr Cameron, "Because Zac Goldsmith is our candidate for London Mayor and he has threatened to resign if I give a third runway at Heathrow the go ahead. I am therefore waiting until after the Mayoral election to announce my decision to go ahead at Heathrow."

*as in Radio 4 Today, although it could just as well have been 'Are you being Served?'