Parts of Great Yarmouth are seeing some flooding as the highest tides for 50 years threaten the east of England.

Thousands of people have been evacuated but the Environment Agency said surge levels were expected to be nearly 8in (20cm) lower than originally feared.

Parts of Lincolnshire, Suffolk, Essex, North Yorkshire and Kent are on alert.

In London, the Thames Barrier was being closed this morning. The Thames has been declared all clear.

Prime Minister Gordon Brown chaired an emergency Cobra committee meeting at 6am this morning.

Phil Rothwell, head of flood policy at the Environment Agency, said the surge was about the same level as the devastating 1953 flood but that technology and sea defences had improved since then.

He said: "It looks to be about 20cm lower than we originally thought, judging by what's happened slightly further north.

"However, that's still above the crest height of some of the sea defences."

The Environment Agency has eight severe flood warnings, 12 standard flood warnings and 23 flood watches in place, mainly in East Anglia, the north east of England and along the south coast.

Environment Agency chief executive Baroness Young said: "I hope our defences can cope but this is a pretty severe weather event and some of them may not."