A potential death blow has landed on Boris Island as the European Investment Bank loaned the London Array wind farm project £250 million.

Hopes were already disappearing for the Mayor of London’s £40bn artificial island airport after the now Transport Secretary Theresa Villiers said the scheme was "not Conservative policy".

Mr Johnson wants to build up to six runways on an island in the estuary two miles off Sheerness in Kent. The wind farm is 12 miles off the coast of Kent.

Now the Thames Estuary project has structural funding, the controversial policy may be killed off.

The London Array will is tipped to become the world's largest wind power generator producing 1GW of energy, enough to power nearly a million homes and save 1.9m tonnes of CO2 every year.

90% of airlines apposed Boris' initiative as an alternative to expansion at Heathrow – BAA has since dropped their plans for a third runway in West London and a second at Stansted. A feasibility study is currently being conducted by Doug Oakervee, Executive Chair of the Crossrail project but there has been concern at his failure to appear at a London Assembly scrutiny meeting.

The Mayor’s Office had previously said "A holistic approach is needed when looking at any future use of the estuary."

"Cornerstone of green future"

Danish firm DONG Energy, who own half of the London Array, called it the "cornerstone in this transition towards a greener future."

The first phase of the London Array wind farm will have a capacity of 630MW and is expected to begin operation in 2012, providing renewable energy for the London Olympics.

Simon Brooks, EIB vice president responsible for the UK, said:

"The European Investment Bank is pleased to be able to support DONG Energy's contribution to London Array, expected to be the world's largest offshore wind farm.

This project will make a significant contribution to meeting both Europe's and the United Kingdom's renewable energy targets."

London Liberal Democrat MEP Sarah Ludford said:

"This European funding is an excellent 'green gift' for Londoners. The windfarm will make the most of our infamous British weather to provide climate-friendly clean energy for the capital."

We need more renewable energy projects such as this one, and the gradual decommissioning of old dirty coal power stations. Not only does wind power provide a carbon-free energy supply, it also carries no risk of deep water oil spills!"

The UK has signed up to the EU Renewable Energy Directive, which includes a UK target of 15 percent of energy from renewables by 2020 - something engineers, from the Institution of Mechanical Engineers called "physically impossible".