The reason the measure is being introduced now is that the advice that we have always had is that there was little point, if any, in introducing quarantine at the border with the R level—the level of the prevalence of the virus—at a high level, particularly above R1. Now that it has come down, and is still coming down even further, it makes sense, as we reduce the level of coronavirus in the UK, to introduce the measure to stop reinfection coming in from people carrying it from abroad, particularly those who would not necessarily be showing symptoms. There will be some flexibility in the detailed arrangements set out, but this will cover, in principle, all people coming in, whether it is to ports or to airports.