Tony Blair gave George W Bush a present on Monday: a bust of Winston Churchill. Apart from looking lovely in the Oval Office, this was intended as a reminder of the special relationship's finest hour, when Britain and the US worked to turn war into peace.

Tomorrow, by contrast, Mr Blair and President Bush will meet at Chequers to discuss Son Of Star Wars. Will history judge this as the moment when the old allies began to turn peace into war?

The US President's plans for a global missile defence system have frightened a lot of people around the world. Those anxieties are heightened here in North Yorkshire, as the US needs to use two of the county's RAF bases, Menwith Hill and Fylingdales, to make the system work. Many argue this is like painting a giant target on the North York Moors and inviting the world's most unstable nations to have a pop at us.

So why has President Bush pressed ahead? As the last remaining superpower, the United States is feeling vulnerable. It believes that "rogue states" are ready to attack America, and many have the capability to do real damage.

The strategic justification by the US military for spending $28 billion on Son Of Star Wars is therefore simple. Self defence. If one of these rogue states, such as North Korea, Iran, Iraq or Libya, attacked America, rockets launched from land or from ships would intercept and destroy the hostile missiles in space. This system could also be used to protect America's allies.

It sounds impressive in theory. In practice, the technology for a process described as "shooting a bullet with a bullet" has faltered. The only anti-missile system tested in combat was the Patriot, deployed in 1991's Operation Desert Storm. Out of 44 fired, most missed their targets: Iraqi Scud missiles.

Tests of the Son Of Star Wars system have also been unimpressive. Two American experts wrote a paper entitled Why National Missile Defence Won't Work, which was published in the Scientific American. No wonder, then, that the Pentagon was so cock-a-hoop this weekend when the system scored its first direct hit in a test conducted 144 miles above the Pacific Ocean.

Washington wants the missile defence system to be up and working by 2005. For that, President Bush needs Britain's blessing for the use of bases at Menwith Hill and Fylingdales.

Menwith Hill, run by the US National Security Agency and employing 1,200 US citizens, is the biggest ear in the world. It can listen to millions of messages a day, and would be expected to pick up any intelligence of a planned attack by a "rogue state".

Menwith Hill is also the European base for America's Space Based Infra Red System, which uses satellites to provide early warning of ballistic missile launches.

Only one US military officer is stationed at Fylingdales, which is run by the British Ministry of Defence. Opened in 1962, it is primarily a ballistic missile early warning station. The famous "golf ball" radomes have now been replaced by phased array radars. If anything is launched, Fylingdales should know about it.

The British Government's official response to America's need to use Menwith Hill and Fylingdales in missile defence has been muted. Ministers repeat the mantra that the US has yet to make a formal approach, so they have not considered their response. This is obvious nonsense.

Many commentators believe the Government is simply playing for time. Tony Blair is minded to give Bush the go-ahead. This would certainly cement Britain's "special relationship" with America, but it would also antagonise many other nations who are vehemently opposed to Son Of Star Wars. By keeping quiet, ministers were hoping that national missile defence would simply go away.

Until recently, that seemed a possibility. Several test failures suggested that the technology was not up to the task - but then came Sunday's success. The defection of Senator James Jeffords from the Republicans to the Democrats in May suggested missile defence might be derailed politically. Yet President Bush is now pressing ahead with renewed vigour. Mr Blair will be compelled to make a decision soon.

The opposition lined up against missile defence is impressive. To go ahead with the project, the US is unilaterally tearing up the 1972 Anti-Ballistic Missile Treaty. This has been the cornerstone of global stability for decades. Russia and China, who earlier this week signed a new alliance treaty, have both been angered by the move. They might respond by increasing their nuclear arsenal, restarting the arms race.

Most of Britain's European allies are wary of President Bush's plans too. Although Spain has come out in favour of missile defence, neither France nor Germany are keen.

In Britain, there is a groundswell of opposition. Earlier this month Greenpeace launched a highly effective protest. People dressed as rockets waddled past security at Menwith Hill, drawing national attention to the base's potential future role in Son Of Star Wars.

At Westminster, more than 250, mainly Labour, MPs have signed a Commons motion expressing "grave doubts" about the project and urging the Government to explore other ways of reducing the perceived threat from "rogue states".

Even in America, support for missile defence is faltering. President Bush's job-approval rating amongst the American people is falling, and now rests at only 52 per cent. And retired Rear Admiral Eugene Carroll, who has spent a lifetime working in US defence, told the Evening Press that "plans by the Bush administration to revive the Star Wars project and upgrade RAF Fylingdales, near Whitby, as a national missile defence base will increase the threat of a nuclear attack". If that attack came, he added "residents in North Yorkshire would have just enough time to put their fingers in their ears".

And that it is why it is here, in North Yorkshire, that the British opposition to national missile defence is focused. We would be first in the firing line. That is why if Mr Blair lends British assistance to missile defence, he will make the world, and North Yorkshire in particular, a less safe place to live.

Updated: 16:51 Thursday, February 07, 2002