A MAJOR new railway line could be built through Brentwood's green belt as part of an ambitious project to create a new airport in the middle of the Thames Estuary.

The line, capable of transporting hundreds of thousands of passengers and millions of tonnes of freight, could connect a multi-runway airport hub built on the Isle of Grain in the Hoo peninsula, to mainline services north of London.

The vision is part of renowned architect Lord Foster's contribution to the plan, which involves miles of land between Tilbury and Brentwood being developed into a state-of-the-art railway line connecting a £50 billion four-runway airport, operating 24 hours a day and capable of handling 150 million passengers a year – more than double that of Heathrow.

One of the many casualties if the plan ever did happen might be Hole Farm in Warley.

Owner Peter Warley, who has farmed it for 40 years but who lost a large chunk when the M25 was built 26 years ago, said: "It is not good news. It's like anything. The M25 went through the farm and there was nothing we could do about it.

"If they want to build a railway, they will. It's just that a little bit more of the countryside will be ruined.

"The green belt is only the green belt until the Government wants it.

"The green belt is meant to be safe. But if they want it they'll take it."

The Government is increasingly warming to the idea of a Thames Estuary airport as it attempts to maintain the UK's aviation hub status and will carry out a detailed consultation in March to develop the idea further.

The plans, backed by Mayor of London Boris Johnson, will concentrate Britain's airport capability to the East and North East of London and seeks to find extra capacity after a third runway at Heathrow was ruled out.

Mr Johnson envisages a similar plan for an island airport off the cost of the Isle of Sheppey, with the site linked by road and railway bridges.

In both cases planes would descend over the North Sea rather than densely populated parts of West London.

Mr Johnson said: "The capital's airports are already full and runway space is at a premium.

"That is why I believe there would be considerable benefit from providing capacity at a new airport which can act as a hub, particularly to the rest of the UK.

"Heathrow is not the answer. Its confined and unsuitable location means it cannot grow to a size comparable to the expanded airports at Frankfurt, Madrid, Amsterdam and Dubai.

"For too long Britain has failed to act, paralysed by the difficulties rather than recognising the opportunities. With jobs prosperity and investment at risk from inertia we must act now."

Lord Foster, founder and chairman of Foster+Partners, said: "These visionary proposals are far from future fantasy.

"They are both essential and down to earth.

"When you look at the eastwards thrust of London's infrastructure, with the Channel Tunnel and the Olympics, you can see how it would be possible to create a 24-hour airport.

"This move would greatly improve the quality of life for Londoners by reducing pollution and improving security.

"It would also allow London to compete with rapidly expanding airports in Europe and the Middle East.

"The arguments are extraordinarily persuasive and the precedents are also compelling.

"More than ten years ago Hong Kong built what was then the world's largest airport at Chek Lap Kok, an island reclaimed from the sea – in just four years."

However, the plans have been dismissed as unrealistic by environmental campaigners.

A spokesman for the Campaign to Protect Rural England said: "We are very clear that we should be investing in rail not airport expansion.

"Even if you think it is able to be built it would need new dual carriageways road and rail links.

"The mind boggles at the expense, never mind the environmental impact this would have."