The UK is toughening its border control to protect the success of its vaccination programme from the new COVID-19 variants.
The UK Home Office announced that people who wish to fly out of the UK will have to provide a declaration stating the reason for their journey, which will be checked by carriers before departure.
It comes as "too many people" are still "coming in and out of our country each day", Home Secretary Priti Patel said on Wednesday.
"The rules are clear - people should be staying at home unless they have a valid reason to leave. Going on holiday is not a valid reason," she said in the House of Commons.
The measure mirrors the checks on arrivals that are already in place with the passenger locator form.
People who don't follow the regulation will face a fine - though the government did not specify the amount.
The Home Office has also said that travellers from countries affected by an international travel ban - and "who cannot be refused entry" - will be required "to isolate for 10 days without exception".
Also, police presence at ports and airport will be increased.
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