I have an idea how the Government could start on the huge spending cuts that will be required after the next election: replace the environment department with a man carrying a sandwich board bearing the message “Prepare to meet thy doom”. He would do much the same job as Hilary Benn but at a fraction of the cost. Yesterday the UK Climate Impact Programme, a quango set up by his own department, published a report predicting the effects of global warming over the next century.

It warned, among other things, of increasing tempest and flood, speeding up coastal erosion. Mr Benn's response? We'll have to redouble our efforts to cut carbon emissions - but there won't be a penny of extra cash for flood and sea defence. Moreover, there was not a hint of any change of policy over constructing thousands of new homes most at risk of river and coastal flooding, in places such as the Thames Gateway.

It was a response that encapsulates the Government's attitude to climate change. It is quite happy to frighten us with grim prophecies of meteorological armageddon but when it comes to practical measures to cope with the predicted effects of climate change, it doesn't want to know.

Whatever happens to temperatures in future there is an urgent need to bolster river and sea defences. As far as London and the South East are concerned, it isn't so much that sea levels are rising as that the land is sinking. That is not going to be reversed by insulating a few more homes and driving electric cars.

That our wealthiest and most populous city is slowly sinking into the Thames Estuary has been known for decades, and yet still we are doing laughably little. In the Netherlands, sea defences are built to defend against the level of flood expected once in every 10,000 years. In Britain, if we build them at all they are constructed only to save us from a once-in-200-year flood. Some parts of the coast, such as Happisburgh in Norfolk, used to have sea defences but have had them removed altogether, the Government ruling against replacement on the ground of cost.

If Mr Benn was discharging his duties properly, he would break off from lecturing us about carbon emissions and start planning at once to replace the piddly little Thames Barrier at Woolwich with a proper barrage, from Southend to Sheerness, like the one the Dutch built across the Zuider Zee, complete with hydroelectric plant. I know it will be expensive, and may even require a few climate change co-ordinators to be made redundant. But compared with the cost of losing London, it will be peanuts.

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