LIKE much of the capital it is all too easy to take the Thames Barrier for granted, but the heavy rains and high tides of recent weeks have reminded Londoners just what a vital defence it is.

Back in 1953 when the project was first conceived, people didn't need reminding of the devastation a flood could bring.

More than 300 people lost their lives during the North Sea flood when defences proved inadequate.

News Shopper: Behind the scenes at the Thames Barrier

Work finally began on a new defence off Charlton in 1974 and, in 1982, the barrier was operational, using a system of 10 gates to hold back the sea, stopping the tide from working against the downstream flow of water over Teddington weir.

Ahead of one closure, News Shopper took a trip beneath the barrier, being led through narrow, cable-lined corridors and out on to one of the piers.

Beneath each pier's wooden, stainless steel-shelled structure, two large cylinders push and pull to control mechanical arms which can haul the gates into place in around 12 minutes.

News Shopper: Behind the scenes at the Thames Barrier

Around 16 people work on each closure from a regular team of 28 - who maintain the barrier while it is not required, performing a test closure each month.

Recently, they have been working overtime, with a spate of consecutive closures which fell just one short of the barrier's record of 14, set in 2000.

Indications of trouble ahead were given back in December when high tides caused pockets of flooding along the east coast in December, but the Thames defences kept the waters at bay.

Barrier boss Andy Batchelor explained: "Later, relentless strong winds and heavy rain fell so across the south-east we've seen major river surges. Their levels have been right up."

News Shopper: Behind the scenes at the Thames Barrier

He added: "Our incident rooms here have basically been 24/7 since well before Christmas."

The barrier, which covers 400,000 properties, 1.5m people and £200bn in asset value, is expected to hold unless there is a 1 in 1,000 event.

A recently released image by the Environment Agency shows the devastation such a flood could cause.

News Shopper: This is the area that may be affected by flooding in a 1 in 1,000 year flood event, if none of the Thames defences, barriers and walls were in place.  It does not reflect the area that would have been affected by the December storm and tidal surge.’

Originally expected to provide defence until 2030, it is now expected to last up until 2070, though Mr Batchelor says a new barrier may eventually be needed further downstream at Tilbury.

In the meantime, developers are advised to keep their properties away from the river.

Sites like the flats near the Woolwich ferry have their units raised high, with their car parks open to flooding. And famous venues such as The O2 and Tate Morden have terraced river walls which allow some storage of rising water.

Mr Batchelor stresses people can find out if their home is on a floodplain at the agency's website, and, if they are, sign up for flood alerts and make plans in case there is a flood.

Visit for details.

News Shopper: The Thames Barrier will be closed from around 3pm until 7.30pm today (Jan 6).

How the Thames Barrier Works

The Thames Barrier has two types of gates - falling radial gates which sit above the river and rising sector gates which lie on the river bed, allowing river traffic to pass through.

Hydraulic cylinders are used to rotate the gates into position.

Individual gates can be closed in ten minutes but the whole barrier closure takes one and a half hours.

The closure usually takes place soon after low tide.

The four main gates span 61 metres and weigh over 3,300 tonnes each.