0211 GMT October 24, 2020
The rufous bush chat was spotted at Stiffkey, north Norfolk, prompting up to 100 birdwatchers to go to see it, according to BBC.
Native to southern Spain, Africa and the Balkans the bird, also known as the rufous warbler and rufous bush robin, is rarely seen in northern Europe.
Dick Filby, of Rare Bird Alert, said it "would have been heading for a tropical climate and went the wrong way."
He said the last time the bird was spotted in Britain was at Prawle Point in Devon in 1980.
"In 1998, one was seen in Jersey (part of the British Isles but not classed as part of Britain)."
Filby said he hoped birdwatchers would be wearing masks and keeping socially-distanced as they enjoyed the view.
Norfolk Police called on birdwatchers to keep to COVID regulations.
Chief Superintendent Chris Balmer said: "People may arrive on their own but some have started to gather in groups larger than six to be able to see the bird. This is a breach of the law.
"In the first instance officers will engage, explain and encourage people to leave but enforcement is an option and we will be issuing fixed penalty notices should people not comply."