Why Heathrow is a test of the Prime Minister's leadership But that was before the threat of a double-dip recession and an increasingly muscular fightback by those sympathetic to the economic case for improving Britain's infrastructure. As George Osborne, a member of the Cabinet less convinced by green-wash government than some of his colleagues, pointedly put it at the Conservative Party conference last autumn: "We're not going to save the planet by putting our country out of business." There is a growing realisation among a small number close to the Prime Minister and an increasingly vocal set of MPs ably led by Kwasi Kwarteng that the Conservatives are going to have to reconsider their "no expansion at Heathrow at any cost" position. Mr Kwarteng, the Tory MP for Spelthorne, itself near Heathrow, has developed policy options around compensating local people adversely affected by any expansion. Such discussion documents will become increasingly important as the Prime Minister and the Chancellor consider their next move. Rather than being a threat to Heathrow expansion, the development of the Thames Estuary option - a new, four-runway airport off the Kent coast - is actually a lifeline. In the past, the options were: expansion of Heathrow or keeping Heathrow as it is. Now the options are: the expansion of Heathrow or its closure. The economics of aviation are such that only one hub airport is sustainable in a country the size of Britain. If the Thames Estuary option is given the green light then, if it is to work, airlines will have to be obliged to move there (despite almost certainly higher landing fees). The threat to Heathrow will then be clear along with the hundreds of thousands of jobs such a significant piece of transport infrastructure supports. One signatory to the letter we publish today is Chris Parker on behalf of Microsoft. Microsoft's UK headquarters is in Reading, a short distance from Heathrow. As a global giant which requires connections to the rest of the world, the site is an obvious plus because of its proximity to Heathrow. The same is true of GlaxoSmithKline in Brentford, West London. If Heathrow goes, what will their attitude be to maintaining a presence in the UK? Might it just be simpler for them to move close to another European hub airport such as Schiphol, Frankfurt or Charles de Gaulle where none of the ridiculous constraints faced by Heathrow exist? Somewhat gingerly, the third runway lobby is starting to show a little ankle. Later this month, Justine Greening, the Transport Secretary, will announce yet another stage of the interminable aviation review which is likely to raise the estuary option. But to have a review without including the one option that has already been investigated and is workable - a third runway at Heathrow - is bordering on perverse, if not legally questionable. As one senior aviation figure put it to me - such a position would be like having a review of supermarkets without including Tesco. Do not expect anything definite at this stage but in the end Heathrow will be put back in the mix. The currency of politics is uncertainty (something that business leaders find hard to grasp) and I am sure Mr Cameron will um and ah for a good deal longer on such a delicate issue. He has privately told colleagues that it is all very well talking about the macro-economic case for a third runway but he will be the one blamed when it comes to tearing down the local church to make way for more airline-friendly Tarmac. But, make no mistake, the case for some leadership and a significant move on Heathrow is starting to encroach on the Prime Minister's thinking. In the Treasury the "Northolt question" has been discussed - whether or not there is anything that can be done to link the RAF runway in West London to the Heathrow complex. It is becoming clear that the UK has a global leader in its present airport provision - a position that is under threat. As with the financial services sector, do we really want to consign that lead to the history books in the search for some ill-defined and ill-thought-out future? BP's gain The settlement of a part of the $40bn (£25bn) legal case against BP in the Gulf of Mexico is good news for investors. Institutional shareholders want certainty and, even if the cost is deemed by some to be a little high, it is better than having the Sword of Damocles constantly over your head. Most importantly, what the deal does is open up the possibility of a deal with the US Government. The Department of Justice would have found it nearly impossible to settle with BP while hundreds of shrimp farmers and the like (all, of course, voters) were still battling through the courts. Now they are off the field of combat, the Government will be encouraged to put in place its own agreement.