In England, the current Day 2 test standard will change from PCR to lateral flow from 4am on Sunday (24 October).

All arrivals, including those who are fully vaccinated against Covid-19, will still be required to complete a Day 2 test.

Tests can be delivered to travellers’ homes, or completed at any of the firm’s 24 regional and airport testing centres.

Results are confirmed in 25 minutes, and will be authenticated once travellers upload a picture of their completed test and their passport number to the ExpressTest app.

The image will be checked by a dedicated team, with official proof of status sent within 60 minutes during hours of operation, which have been extended from 8am to midnight daily.

The app has been designed to recognise a unique QR code identifying each test, and features both a guide to completing the test and a timer.

Christian Corney, Cignpost ExpressTest chief executive, said the company had invested "significantly" in its LFT testing process, including in a "robust" and "secure" app.

"Our network of testing centres will be invaluable to fully vaccinated tourists and business travellers from other countries, who might find it difficult to receive tests through the postal service and want another option that is simple and secure," Corney added.