Police wielding batons clashed with protesters last night when a demonstration against George Bush's farewell visit to Britain turned violent a few hundred metres from where the US President was dining with Gordon Brown.

Within the shadow of the Houses of Parliament, officers dressed in riot gear skirmished with several hundred demonstrators who had been attending a rally organised by the Stop the War Coalition.

The Metropolitan Police said 25 protesters were arrested. In some cases, squads of police in riot gear had swooped upon individual demonstrators , picking out their target then barging through the crowd to detain them.

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Police drew batons and truncheons in an attempt to push back a crowd which at 6.20pm moved from the rally on Parliament Square to try to gain entry to Whitehall. A squad of riot officers and horses were later sent to reinforce the barricade as protesters chanting "George Bush, terrorist" and "Bush go home" repeatedly tried to break through the reinforced crowd barriers and concrete blocks.

The decision to close Whitehall while Mr Bush and his wife, Laura, dined with Mr Brown and his wife, Sarah, was condemned by campaigners and the Liberal Democrats as an example of civil liberties being curtailed at the request of a foreign government.

The clashes were in stark contrast to Mr Bush's arrival in London at the end of a week-long tour expected to be his last in Europe before he leaves office.

A grand total of 28 protesters from the Stop the War Coalition gathered at Windsor, where Mr Bush had tea with the Queen.

Iqbal Siddiq, 26, a student at the Windsor protest, said: "The message is good riddance. He's still the mass murderer-in-chief. But ... he's yesterday's man. Everything he did to engineer the war in Iraq still makes me angry but it is fast becoming history. We've got to concentrate on the next guy and the mess Bush has left behind."

Mr Bush became the first US president to be hosted at Windsor since Ronald Reagan in 1982. Buckingham Palace confirmed the couple had shown particular interest in a suit of armour worn by Henry VIII.

Whether this aside sparked a conversation about the perils of foreign invasions or armed combat will go unrecorded by history but more serious matters awaited Mr Bush as some of the 1,000 police deployed at a cost of £1m to ensure his security took up positions among the trees and on turrets with rifles and sub-machine guns.

But it was the closure of Whitehall by Scotland Yard and its implications for civil liberties that provoked the strongest feelings. A Stop the War spokesman, Andrew Burgin, said: "What would the Americans think if Gordon Brown turned up with a 700-strong entourage who told them to close down central Washington? It is the sort of high-handed attitude that has been shown by Bush all along."