Edinburgh saw up to 180,000 party-goers from around the world arriving to join the UK's biggest street party as the Scots celebrated Hogmanay.
In London, 100,000 people converged on Trafalgar Square to see in the New Year to the chimes of Big Ben.
Revellers everywhere had to wait a little longer to celebrate the arrival of 1999 - scientists have ruled that the last minute of 1998 should be 61 seconds long to allow the rotation of the Earth to catch up with today's super-accurate atomic clocks.
Shoppers having stocked up massively for the Christmas period, surged to retail centres again yesterday to make last minute purchases. But few people seemed inclined to cook, with large numbers of the capital's restaurants fully booked. At Sir Terence Conran's restaurant, Mezzo, which seats nearly 500 all the tables were booked twice. Diners who arrived at 7pm had to give up their tables by 9:15, although they were allowed to continue their evening at the bar.
The well-organised booked taxis well in advance, realising that most city centres would be snarled up well into the early hours. And firms were each reporting several hundred bookings in advance.
In Edinburgh, the former GPO building on Princes Street was turned into a massive warehouse party. The street party and Concert in the Gardens lasted until 1.30am, with free buses taking revellers home.
Revellers in Northern Ireland were also taking to the streets at press time. In Belfast, what is expected to be the city's biggest street party featured two open air concerts by the Saw Doctors and Downpatrick band Ash, a firework display and a funfair.
More than 10,000 people were expected and council chiefs said it would be a dry run for the Millennium celebrations: "In the future we would like Belfast to be even better than Edinburgh at New Year," said a city council spokesman.
As the nation wakes up to a collective hangover it should be well equipped to cope: sales of headache cures soared last year with the total bill for over-the-counter painkillers coming to pounds 267m.
Cardiff plans to stretch New Year over three days, as a pilot project for the Millennium celebrations. Last night it laid on a funfair, a lantern procession, New Year resolution trees, live bands and a fireworks display. Council leader Russell Goodway said: "Cardiff is gearing up to mark the Millennium with a family celebratory event we can all participate in and be proud of."
London has assembled more than 10,000 performers for the capital's 13th New Year's Day parade. Some 800,000 spectators lined the streets last year to watch the three-hour jamboree. Organisers predict there could be more than one million today if the weather is good. Bob Bone, the director of the parade, said it would be "the biggest street entertainment to take place anywhere at any time the of year".
"We are serving up a feast of family entertainment and the interest from around the world this year has been immense."
New York's Thanksgiving Parade, organised by Macy's department store, is the London spectacle's nearest rival and featured 5,000 performers last November.Reuse content