All pubs, bars, restaurants and other hospitality venues in England must have a 10pm closing time since Thursday, to help curb the spread of coronavirus.
The sector is also restricted by law to table service only.
The measures were set out by Prime Minister Boris Johnson on Tuesday. It came as the UK's COVID-19 alert level moved to 4, meaning transmission is "high or rising exponentially".
The government's chief scientific adviser Sir Patrick Vallance warned there could be 50,000 new coronavirus cases a day by mid-October without further action - which, he said, could lead to more than 200 deaths per day by mid-November.
On Monday, a further 4,368 daily cases and 11 deaths were reported in the UK. There were 3,899 cases reported on Sunday.
Scotland, Northern Ireland and Wales have also introduced tighter measures.
The new measures are not popular. The government must be transparent about its reasons for any future coronavirus lockdowns and “justify” its interference with public freedoms, Ministers of Parliament have said.
The warning was issued by parliament’s Joint Committee on Human Rights following the new curbs to stop a rapid rise in infections.