Thanks. An interesting if nuanced point will be if one is allowed to test on arrival to the UK if coming from a travel corridor country (for less than 14 days) when one has been 5 days out of a "red" country. I wouldn't think so from the press release, but we will see.

The real benefit would be to business travelers and tourists. A UK resident can cover the 5 days in a long weekend at home, but there will be few visitors coming in if the first part of the trip is 5 days spent staring at a hotel room wall. However, if a business traveler could spend a 5 day break in, say, Dubai, and then come in to the UK and promptly be tested and released, there would definitely be takers, myself included. And if the traveler has been in an epidemiologically safe country during those 5 days (ie one on the travel corridor list), this shouldn't appreciably increase transmission in the UK (it's a different story for the stopover destination).