Suppose that you went to the Dentist and were told that prior to any treatment you would need an HIV test, even if you had one last week on your previous visit to the Dentist and even if you were an 80 year old spinster.
Our approach to Borders Control is as ludicrous as this, and meant to be. We've simply borrowed a system from the old Soviet Union and enhanced it with technology (eye scanners, passport scanners) which are slow or simply don't work.
Airline passengers are a huge body of people and their movements and character are highly predictable. Huge amounts of information are available on them before they fly. They have had to show passports and visas to get on planes.
I recall that when fifteen years ago I flew to Kyiv with BA, the airline checked everyone's passport for a Visa before we boarded; they didn't want to have to bring anyone back. The Visa check at the other end was redundant, but it was carried out by a man with an awful lot of gold braid on his cap.
99.99% of what goes on at UK Border Controls is wasted labour. It is utterly pointless to scan the passport of every Brit returning from a package holiday on a charter flight or an easyjet or Ryanair flight. They are all Brits, for goodness sake, and it is predictable that they all have perfectly good passports. They only left the country ten days ago and if they had good passports then, then it's pretty certain that's what they have now. They are entitled to re-enter the country of which they are citizens without being hassled and delayed.
The manpower at Border Controls is being wasted, Soviet-style. Ninety nine percent of them should be engaged in intelligence-gathering activities designed to identify the tiny number of people who really need to be stopped at the Border, checked and maybe sent away again. This involves discrimination: it means using judgement and going after the people who really shouldn't be coming here, even if they all look the same. It means getting on the plane when it lands, not corralling everyone later in sheep pens. It means putting through a phone call before a flight leaves and telling the other end you won't accept passenger X so they may as well get off now.
It is a pitiful state of affairs to hold everyone at the Border so that it doesn't look like discrimination when you hold one person. It's equivalent to telling the 80 year old spinster she has to have an HIV test before she can have dental treatment.
You should be allowed to act on probabilities. The Home Office idea of collective punishment for everyone is simply not acceptable.
Open the Borders and let people in! Ninety nine point nine nine percent have every right to be here. Find some other way of stopping the 0.01 (or 0.00001) who shouldn't be.