The UK has seen off 2020 and celebrated the dawn of 2021 with a fireworks and light display over London that included tributes to NHS staff.
Revellers were not able to ring in the New Year in the usual way because of the coronavirus pandemic, with people instead told to stay at home.
Police had to break up various parties and events across England overnight.
Forces have handed out hundreds of fines, with several issuing the maximum £10,000 to event organisers.
Much of the UK saw in the new year while under lockdown rules, with about 44 million people in England - or 78% of the population - in tier four, the top level of Covid restrictions.
Mainland Scotland, Northern Ireland and Wales are also under lockdown.
Although people were warned not to attend any parties outside their own homes, there were many around the country who ignored the rules.
The Metropolitan Police said police attended 58 parties and unlicensed music events in breach of tier four rules across London overnight, the vast majority of which ended when police intervened, they added.
Fixed penalty fines were given to 217 people while five others could be fined £10,000 for organising large gatherings. The police force said four other people were arrested for breaching Covid regulations by gathering in central London.
Elsewhere, other forces also broke up parties and handed out hundreds of fines. They included Greater Manchester Police, which issued 105 fixed penalty notices at house parties and larger gatherings. And Leicestershire Police had to issue six on-the-spot £10,000 fines to party organisers.
In Essex, hundreds of people were dispersed from an illegal New Year's Eve party at a church, while Lancashire Police broke up a party in Hyndburn, near Blackburn, attended by 80.
Meanwhile, in Scotland, Edinburgh's traditional Hogmanay street party was cancelled, with videos of a drone display released instead.
The series of videos showed a swarm of 150 lit-up drones over the Scottish Highlands and Edinburgh were released, which organisers said it was the largest drone show ever produced in the UK.
Despite the cancellation of Edinburgh's traditional Hogmanay celebration - which normally attracts 100,000 people on the city's streets - there were some people who ignored the pleas to stay at home.
Crowds of several hundred people gathered at Edinburgh Castle to see in the new year. They sang Auld Lang Syne and danced before eventually dispersing when several police vans and cars pulled on to the castle esplanade.
On New Year's Eve, Health Secretary Matt Hancock called on people to take "personal responsibility" and stay at home to avoid spreading Covid-19.
London's 10-minute display over the Thames aired on the BBC at midnight, and began with a poem which addressed the pandemic, that said: "In the year of 2020 a new virus came our way; We knew what must be done and so to help we hid away."
Light projections lit up the sky over the O2 Arena, including the NHS logo in a heart accompanied by a child's voice saying: "Thank you NHS heroes".
The show also recognised Captain Sir Tom Moore, who raised £33m for the NHS by walking laps of his garden and the Black Lives Matter movement. One 2020 phenomena - working from home - was represented with a mute logo backed by a voiceover saying "You're on mute".
The display ended with a call from Sir David Attenborough about the need for action on climate change.
In a speech being broadcast on BBC One between Doctor Who and EastEnders this evening, Sir David will say that this "could be a year for positive change - for ourselves, for our planet and for the wonderful creatures with which we share it".
Despite the "challenging" times we live in, "the reactions to these extraordinary times has proved that when we work together there is no limit to what we can accomplish", he will say, as he looks ahead to the United Nations Climate Change Conference later this year.
Official figures showed 10.75 million viewers watched the 2021 New Year celebrations on BBC One. It's down from the 11.18m who saw in the start of 2020 on the channel.
Mayor of London Sadiq Khan said he was proud of the show, which he said "paid tribute to our NHS heroes and the way that Londoners continue to stand together".
"We showed how our capital and the UK have made huge sacrifices to support one another through these difficult times, and how they will continue to do so as the vaccine is rolled out."
Usually, around 100,000 people pack into the streets around Victoria Embankment to watch the New Year's Eve fireworks.
In his New Year's message, the Archbishop of Canterbury said he saw "reasons to be hopeful for the year ahead" despite the "tremendous pain and sadness" brought by 2020.
The Most Reverend Justin Welby spoke of his experience volunteering as an assistant chaplain at St Thomas' hospital during the pandemic, saying: "Sometimes the most important thing we do is just sit with people, letting them know they are not alone."
In his message, filmed at the London hospital and broadcast on BBC One on Friday afternoon, he said: "This crisis has shown us how fragile we are. It has also shown us how to face this fragility.
"Here at the hospital, hope is there in every hand that's held, and every comforting word that's spoken.
"Up and down the country, it's there in every phone call. Every food parcel or thoughtful card. Every time we wear our masks."
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