Tony Blair has set London's millennium wheel in motion as part of the celebrations to welcome the new century.

The UK prime minister fired a laser beam across the Thames to officially open the new 450ft London Eye landmark.

It will spin slowly all night as the party continues around it - although there are no passengers on board after last-minute checks discovered that one of the 32 passenger capsules was unsafe.

The event was marked by deafening fireworks and a fly-past by British Airways' flagship jet, Concorde.

Before pressing the button Mr Blair said: "To everyone here and throughout Britain, have a happy and wonderful New Year.

"From us all here in Britain to people throughout the world, we wish you peace, we wish you prosperity in the new millennium."

The Queen, en route to the Dome, stopped off at Southwark Cathedral for a service highlighting the religious significance of the millennium celebrations.

She also met some of the poorest people in society at a nearby homeless shelter.

She then sailed down the River Thames to light a huge millennium beacon afloat on a barge, triggering off a string of gas-powered beacons across the UK.

Meanwhile police were preparing for up to four million party-goers in central London alone.

Crowds are thronging into the centre of London - which is to see the centrepiece of the UK's celebrations - with tens of thousands gathered in Trafalgar Square and the royal parks.

Thousands more are already gathering on bridges across the Thames ready for the midnight fireworks and pyrotechnic displays which will appear to set the river ablaze.

In another last-minute hitch, disgruntled guests for the opening ceremony at the Millennium Dome were forced to queue for up to seven hours to collect their entry passes.

An administrative fiasco meant that about a fifth of the 10,500-strong audience did not receive their tickets through the post, and several hundred had to turn up at Stratford railway station, east London, to collect their tickets in person.

Culture Secretary Chris Smith said two ministers had gone to the station to ensure the distribution of tickets went smoothly.

He added that the government was prepared against any potential strike by the millennium bug.

"We're ready for anything that could happen - we've made all sort of emergency preparations but we hope none of them will be necessary," he said.

Scotland Yard have reported no major transport problems, although police decided to close central roads early to prevent traffic congestion as drivers tried to take their cars into the centre.

Blackfriars and Waterloo bridges have been closed. People are being warned to leave their cars at home and travel by public transport.

There are some 6,000 police on duty in central London alone. Home Secretary Jack Straw said he was confident forces would be able to cope.

More than 10,000 beacons are being lit across the UK to herald the new millennium.

The first was set alight on the most northerly Shetland Island of Unst, marking the start of a spectacular firework display.

Beacons in all four UK capitals will be lit at 2145 GMT, with London's being ignited by the Queen.

The £758m Millennium Dome will be officially opened minutes before midnight by the Queen.

"This truly remarkable structure and the Millennium Experience inside it have achieved world-wide recognition as symbol's of the United Kingdom's creativity, inventiveness, and focus on the future," writes Mr Blair in the programme for the opening night.

The New Millennium Experience Company's chief executive, Jennie Page, said the atmosphere within the Dome was "quite nervy" in the countdown to the official opening, but everyone was very excited.

Highlights of the Dome programme include performances from the English National Opera Orchestra, music from Jools Holland, The Corrs and Mick Hucknall and prayers read by the Archbishop of Canterbury and three Barnardo's children.

After midnight, two "aerealists" will perform an acrobatic ballet on bungee ropes high above the audience.

An estimated 180,000 revellers will pack Edinburgh's streets to see in the New Year with Scotland's largest ever Hogmanay.

In Cardiff, a concert by Welsh band the Manic Street Preachers is the key event in Wales' millennium celebrations.

In Belfast and Londonderry huge crowds gathered for a night of musical festivities while in Omagh, where 29 people died in the August 1998 bomb, children lit a millennium beacon.

Around England, events range from a Cliff Richard concert in Birmingham to a lantern procession through the streets of Newcastle upon Tyne.