The sinking of Boris Island

Boris Johnson has spent the best part of six years and millions of pounds of public money in promoting a new hub airport in the Thames Estuary.

He has chaired committees, toured the globe and even captained a ship from Tower Bridge to Kent to visit the proposed sites.

With a few clicks of his keyboard, Sir Howard Davies today ruled all of that work null and void.

Johnson's first choice of a purpose-built island airport in the Estuary does not even get a mention in the airports commission's report. His second choice of an airport on the Isle of Grain has also failed to make the shortlist.

Even expansion at Stansted, which Johnson wanted put under the microscope for £3 million of taxpayers' money, has been ruled out by Davies.

Unlike most victims of ritual humiliation, Johnson was at least offered some consolation by Davies. Put under pressure by the government to avoid a full on confrontation with the mayor, Davies today inserted a couple of paragraphs suggesting that he will study the Isle of Grain proposals for possible future inclusion on the shortlist next year.

The result of that extra study is a foregone conclusion. The estuary airport will always be a total non-starter.

Coming in at roughly five times the cost of alternative proposals, the scheme is vehemently opposed by local Conservative MPs and councillors in marginal seats. Even if those two major problems could be dealt with, the scheme would also involve the closure of Heathrow and London City Airport and the export of hundreds of thousands of jobs from London to a rural area of Kent.

And that's even before you consider the almighty battle it would face from every environmentalist and bird-watcher within a 200 mile radius.

Of course nothing is impossible. If there was a prime minister suitably determined or unhinged to attempt it then it could still happen.

But there's only one politician who would be brave or stupid enough to do that and right now he's sitting nursing his wounds in City Hall.

The Battle of Heathrow

The real battle lies west of London. Proposals to expand Heathrow have been around for decades, but remain unfulfilled for the simple reason that it would be incredibly politically difficult to do.

Building a third runway would involve shifting thousands of people from their homes and closing one of the busiest roads in the country. It would blight millions of west London residents with more aircraft noise and increase traffic congestion in one of the most congested areas in the UK.

And while local public opinion is fairly evenly split on expanding Heathrow, most London politicians are overwhelmingly opposed. It is partly because of this opposition that Boris Johnson got himself into such a mess with his estuary airport proposals in the first place.

However, there also remains a formidable lobby in favour of expanding Heathrow and it is a lobby that appears to have successfully persuaded chancellor George Osborne. The claim that Heathrow expansion is the only viable option for the UK economy was a persuasive one for the last Labour government and it has proved persuasive once again.

But if the government does reverse its opposition to Heathrow expansion then it would be a huge political and electoral risk. Putting off that decision until after the next election today looks much more difficult.