Thamesmead, a former marsh, with its 45,000 residents would be four metres under water twice a day but for London's sea defences. The Isle of Dogs, containing some of the most expensive real estate in Britain, would be just 2.5 metres below each high tide, enough to drown anyone who could not reach first floor level.

These are just two examples of how 1.2 million Londoners - and property developers - protected behind the  Thames barrier, and a number of other sophisticated sea defences, have forgotten that they live below sea level.

But fortunately for them someone is worrying about the future. When the barrier becomes out of date in 2030, rising sea levels, increases in storms and tidal surges, and river flooding caused by intense rains, mean time will have run out for London's sea defences.

It takes 30 years to plan and build civil engineering projects on the scale required to deal with the threat to London, so the problem has already become urgent. Sea levels are rising at six millimetres a year.

A team of 15 has been set up by the Environment Agency and Thames, Anglian and Southern water companies to produce plans to protect existing settlements along the 212 miles of the Thames for the rest of the century.

The team also has to accommodate the government's cherished plans to relieve the south-east's housing crisis by building a new settlement called Thames Gateway - also below the high tide level. This is controversial since building on the flood plain is against government policy, but the new settlement will have 120,000 homes below sea level.

The current estimate of the cost of new work needed between 2015 and 2035 to save London from flooding is £4bn, but that is only a best guess before detailed plans are available. It could be far more.

Among the schemes being considered are raising homes on stilts; building Bangladesh-style cyclone escape roads on embankments above the flood level for new communities like Thames Gateway; and sacrificing large areas of Kent and Essex farmland to flood waters during a tidal surge to prevent London defences being overwhelmed. This last measure, called “controlled inundation”, is being adopted in Holland and Belgium to save towns which would otherwise be vulnerable.

Current defences in London are built to the highest standard in the world - a one in 1,000 chance of the defences being overwhelmed. The Thames barrier, completed in 1982, 29 years after the great flood of 1953, which killed 307 people, was designed to protect the capital until 2030. Its designers claim only a storm or tidal surge severe enough to occur only once in 1,000 years could currently flood London. But with climate change those odds will become considerably shorter and a new scheme will be needed to extend its life and height. All the associated eight barriers and flood walls will have to be raised too.

Sarah Lavery, who is in charge of the project to protect London, said: “It sounds like a very small risk, but if London flooded the consequences are almost unthinkable. There are 38 underground stations that would fill with water, eight power stations, 16 hospitals and 400 schools, plus 500,000 properties. Imagine the economic disruption on top of that.”

She said one of the problems facing the Thames was that it was now a great deal narrower than in Roman times. This meant the tide that reached Teddington Lock to the west of London was trapped in a narrow channel, and if there was heavy rain bringing large quantities of river water over the weir, flooding was likely.

Last January there was so much rain that the Thames barrier had to be closed a record 19 times to prevent the tide and the flood water meeting.

Many of the properties on the banks of the river are already in the river flood plain and have a series of walls, flood boards and other devices to hold back the peak tides.

Ms Lavery said: “We have a choice of building walls that will hold back the river, but obscure the view, or adapting properties so they can put up temporary barriers when a high tide threatens. Most property owners in west London who are already vulnerable to flooding have opted for temporary barriers, but in future that may not be enough.”

For homes on islands in the Thames, Eel Pie Island for example, where flooding is already a problem, the agency is considering a scheme to raise existing homes on stilts.

“It seems to us that in the future it is going to be impossible to protect all these houses. Some are already on stilts, and I think we may be able to make these taller and others we may be able to lever upwards,” said Ms Lavery.

Downstream, where the government is keen on new housing on brown-field sites well below sea level, the agency's plan is to make the river wider, with parkland along the banks to take flood water.

The Government has given financial backing to build a new bridge at Thamesmead, saying it will provide tens of thousands of new jobs.

The six-lane bridge, linking Thamesmead with Beckton at Gallions Reach, would provide a vital transport link for east Londoners, with improved access to jobs and housing, the Department for Transport said.

The decision was welcomed by the Mayor and Transport for London, but the London Greens condemned the decision, saying the road would increase pollution and congestion.

Although a final design has not been confirmed, the structure will be some 40 to 70 metres high, so as not to disrupt the London City airport flight path and still allow boats to pass underneath.

Two lanes are planned each way, with separate lanes for buses and cycles, as well as footpaths.

A public inquiry is expected to start early next year and the bridge should be built by 2013 or 2014.

The £450 million cost of the Thames Gateway bridge is to be met through funding from Transport for London, tolls and Government Private Finance Initiative credits.

TfL wants to build it in partnership with a private company under PFI rules.

London Transport Minister Tony McNulty said the bridge would encourage significant growth in the local economy.

“It would not only provide a much needed boost to the local economy, but stand as an impressive landmark representing a positive future for the Thames Gateway region,” he said.

TfL claims the river crossing would put 600,000 more jobs within 45 minutes of Thamesmead by private or public transport, and create 25,000 new jobs on both sides of the Thames.

Mayor Ken Livingstone said the decision reflected several years of preparation work, including consultation that saw 460,000 leaflets sent to residents asking their views.

Mr Livingstone also said it showed the commitment of City Hall and central Government to deliver better services for Londoners.

But Darren Johnston, Green candidate for Mayor, said funding the bridge would take up a huge slice of the money available for transport projects in London.

“This would be better spent on other improvements for public transport.”

Mr Johnston said the crossing should have been limited to rail and pedestrian use only and that the proposed bridge would become jammed with vehicles travelling from outside of the local area.

Did you know that Downing Street stands on the site of a former brewery? Or that Number 10 was originally Number 5? Or that the last private resident of Number 10 was a Mr Chicken? Read on to find out more fascinating secrets about the long history of th

Are there ghostly goings-on at Henry VIII's palace, or is that hazy image of a fellow in fancy robes just a bit of Christmas cheer? Closed-circuit security cameras at Hampton Court Palace, the huge Tudor castle outside London, seem to have snagged…

LONDON, Dec. 18 — Energy companies plan to erect more than 1,000 turbines off England's coast in a $12.4 billion project to build the largest source of wind energy.

The wind farms, which received preliminary approval on Thursday, would generate as much as seven gigawatts of electricity — enough to supply four million households, or to meet 7 percent of Britain's energy needs. Britain has pledged that 10 percent of its energy will come from renewable resources by 2010.

The Crown Estate, which controls British public lands, including its seabeds, asked companies to submit bids for coastal wind farms in July.

Royal Dutch/Shell, Warwick Energy, Powergen and Total are among companies that won leasing rights of up to 50 years for the project, which involves 15 sites and is expected to start generating electricity in 2007.

The project is vast. Groups of hundreds of turbines will be installed in the shallow waters of the Thames Estuary, in the East Coast area known as the Greater Wash, and off the northwest coast of England.

“This is a massive development for our industry,” said Marcus Rand, chief executive of the British Wind Energy Association. “This puts the United Kingdom in the fast lane to becoming a world leader in offshore power generation.”

Before they can start building, energy companies need clearance from the public and the government, including environmental regulators. The turbines will be visible from the shore only on very clear days, the companies said, so that public outcry, at least about the view, is expected to be minimal.

The project's biggest obstacle may come in the form of a small waterfowl related to the American loon, the red-throated diver, which feeds in and around some of the sites. The Royal Society for the Preservation of Birds issued a cautionary statement on Thursday, asking the government to make sure the wind farms do not pose a “significant threat to birds.”

Little definitive research has been done on the effect of offshore wind farms on the bird population.

“We're in a sort of Catch-22, because we have to prove that this project is not a danger to birds” but there is no project of its size to compare it to, said Peter Crone, a director of Farm Energy, a renewable energy specialist that is one of the winning bidders.

Of course, birds have died after colliding with turbines. “Clearly, birds have been flying into things for hundreds of years, and that hasn't caused any extinctions,” said Dr. Mark Avery, director of conservation for the bird preservation group, one of the strongest environmental lobbies in Britain, one that supports renewable energy, including the development of large, offshore wind farms.

But, he pointed out, it might not make great sense “to construct a large number of objects where large numbers of birds are already flying.”

The famous Frost Fair known to William Shakespeare is returning to Bankside on Monday after a 189 year break.

County Hall is a London landmark and former home of the capital's government.

A GBP500,000 government grant, to be matched by the British Council, is awarded to the British Museum.

I should be grateful to hear from any of your readers who remember minewatching along the River Thames and at the entrance to the Medway, during either the Second World War or the Cold War.

Enemy mines may have been planted in the river by parachute or by other means with the object of striking and sinking shipping using the waterways.

The minewatchers were a largely unsung group of people whose task it was to look out for, plot and report any mines seen floating in the water, so they could be disposed of safely before coming into contact with friendly shipping.
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Sadly, during the Second World War, a number of vessels struck mines in the river.

The minewatchers operated from observation posts at intervals along the riverline. From these they plotted the mines with the use of primitive-looking metal sights. In the widening river, they worked from moored barges and other vessels.

Any information received from readers will help me take a new look at the history of the defences of the Thames.

The results will be included in an entirely re-written third edition of the book Defending London's River.

If you know anything, no matter how little or how much, call me on 01474 323415.

Victor Smith Thames Defence Heritage Northfleet