The three lab tests that would prove I do not have Covid and therefore am not a risk? The same extra steps that the UK government have themselves set out?
Your point about ICU beds is totally moot, too, because if I was carrying the virus I would not be allowed into England, let alone Wales. As OP says, once I have proved that I am not a risk, what is the difference between me going to Wales and Joe Bloggs from Bristol or Brighton?