If Zac Goldsmith is standing again, what is the point of his resignation?

Quite a few MPs are driven by a strange need for validation, but Zac Goldsmith might be the first politician in history to ask his constituents to vote for him three times in two years. Once as Mayor (the less said about that tawdry campaign the better) and, it seems, twice as MP for Richmond Park. He always said he’d resign and trigger a by-election if the Government approved Heathrow, as it did this morning. Originally his threat had force because Richmond was a Tory-Lib Dem marginal and his resignation would mean that the Tories would probably lose a seat. It was Richmond’s way of saying to the Tories: ‘Yes, we’ll vote for you – but only if people like Cameron and Theresa May are being honest about their opposition to a third runway. And if you, Tories, then damage our quality of life with a third runway, then our support vanishes immediately.’