The whole of the UK is back under a coronavirus lockdown.
England and Scotland joined Wales and Northern Ireland by introducing national restrictions on Tuesday.
The UK reported more than 50,000 daily coronavirus cases on Monday for the seventh day running, while hospital admissions have passed the level of the peak last April.
Johnson said hospitals were under “more pressure from COVID than at any other time since the start of the pandemic”.
According to the government, people must remain inside except for essential medical need, shopping for food, exercising once a day or working if it cannot be done from home.
Schools have been closed to most pupils in England, Scotland, Wales and Northern Ireland.
Watch: Boris Johnson announces new lockdown in England