Under level three, the virus is considered to be “in general circulation” and there could be a “gradual relaxation of restrictions.”
Previously transmission was considered to be “high or rising exponentially”.
Health Secretary Matt Hancock said the change was “a big moment for the country” and showed that the government’s plan was working.
The decision to reduce the alert level followed a recommendation by the Joint Biosecurity Centre, the chief medical officers for England, Scotland, Wales and Northern Ireland said.
“There has been a steady decrease in cases we have seen in all four nations, and this continues,” the medical officers said in a joint statement, carried by the BBC.
But they warned it “does not mean that the pandemic is over” and that “localised outbreaks are likely to occur.”
“We have made progress against the virus thanks to the efforts of the public and we need the public to continue to follow the guidelines carefully to ensure this progress continues,” they said.
Two factors determine the UK’s alert level. They are:
COVID-19’s reproduction (R) number, a scientific measure of how fast the virus is spreading
The number of confirmed coronavirus cases at any one time
Mr Hancock said recent progress in both factors showed “a real testament to the British people’s determination to beat this virus.”
There are five coronavirus alert levels in total.