Police had to break up parties across England as revellers ignored warnings to ring in the new year with members of their own household only.
Several forces issued the maximum £10,000 fine to organisers as they battled to get people to stick to the rules.
New restrictions which came into effect at midnight on December 31 meant a total of 44 million people – 78% of the population of England – saw in 2021 under the toughest Tier 4 measures.
The Metropolitan Police (MPS) said officers had broken up a music event in east London's Royal Docks and slapped the host with the top penalty.
A large unlicensed music event has been shut down by officers tonight in Royal Docks. Arrests made and considerations being given for a £10,000 fine for breaches of #COVID19 legislation. #HandsFaceSpacepic.twitter.com/p2wfTi66Xf
— Newham MPS North East BCU (@MPSNewham) January 1, 2021
A number of house parties were also dispersed across the east of the capital.
MPS Barking and Dagenham tweeted just before 2am: "Officers have been attending a number of reported breaches house parties. Several Fines have been issued at various parties across East Area tonight for Covid Breaches."
In Essex, officers dished out more than £18,000 in fines to organisers of unlicensed music events, reporting that hundreds of people had turned up in breach of lockdown rules.
Assistant Chief Constable Andy Prophet thanked all those who had stayed home on what is traditionally one of the busiest nights of the year.
But he added: "Unfortunately, there were others who decided to blatantly flout the coronavirus rules and regulations and, ultimately, they decided that partying was more important than protecting other people.
"We've seized their equipment, arrested five people, and issued a large number of fines to those who think this behaviour is acceptable."
Sussex Police issued 12 fines in Brighton for breach of lockdown rules, and by 11pm had made 13 arrests across the west of the county for a number of offences including affray.
We have issued 12 fines in #Brighton and made 13 arrests in West Sussex for offences including affray.
Our officers will shut breaches down and take enforcement action where necessary. pic.twitter.com/M7E7ZDbtWS
— Sussex Police (@sussex_police) December 31, 2020
"Our officers will shut breaches down and take enforcement action where necessary," the force tweeted.
Detective Chief Constable Terry Woods, of Lancashire Constabulary, said officers had dealt with "a steady stream of incidents" including shutting down a house party in Hyndburn.
He tweeted: "Some shockers tonight e.g. Hyndburn rural property with about 80 young people there @LancsPolice stopped it & organiser reported for £10k fine."
At around 2.30am, he posted: "Demand now increasing – themes assaults, house party fights, sadly domestic abuse & people reaching crisis.
"I spent strike of midnight on foot with cops searching for a high risk missing person. Just resuming from assisting with the arrest of a violent drink driver – welcome to 2021!!"
Demand now increasing-themes assaults,house party fights,sadly domestic abuse & people reaching crisis.I spent strike of midnight on foot with cops searching for a high risk missing person.Just resuming from assisting with the arrest of a violent drink driver – welcome to 2021!! pic.twitter.com/krApIsro2k
— DCC Terry Woods (@DCCWoods) January 1, 2021
West Midlands Police were also battling lockdown fatigue as 2020 drew to a close.
Chief Constable Dave Thompson posted: "Very grateful for time with @OSU_WMP.
"I am afraid some shocking Covid breaches with very large house parties. Well dealt with by the team. Always a pleasure to spend time with such professional officers."
Merseyside Police got ahead of the game by putting a dispersal zone on the Pier Head and other parts of Liverpool city centre between 7.30pm on New Year's Eve and midday on January 1.
The order came just hours after a post was circulated on social media encouraging people to meet near the Liver Building for a party with the words "F*** Tier 3", the Liverpool Echo reported.
Chief Inspector Peter Clark said: "Previous gatherings in Liverpool this year have involved several hundred people showing a lack of social distancing and also led to disorder earlier this year at the Pier Head.
But he added: "The overwhelming majority of people in Merseyside have made huge sacrifices throughout this pandemic, to keep those most vulnerable safe and protect the NHS and other emergency services."
Other forces got off more lightly, with Wiltshire Police reporting "a quiet and peaceful New Year" – issuing around 20 formal warnings for house parties to disperse.