Covid passports

Can anyone explain to me how showing evidence of a negative lateral flow test works?

Surely unless you actually do it in front of the person checking you in (clearly not feasible if there are long queues), you could just use someone else's result? Or just lie?

Because if/when everyone abuses the system, they will stop accepting lateral flow test results as proof of a negative test, as I understand they have done in some EU countries.

I don't really understand what this country's obsession is with gaming the system (and this isn't a dig at you, Sue, as I know it's a genuine what-if...). Ever since the pandemic started, people have gone on about ways of getting around the restrictions - "I'm exempt from wearing a mask"; "I'm going to put my house on the market so my mum can come to view it"; "my hairdresser is in my bubble" etc. It's this constant aim to find loopholes instead of using some common sense that has made the rules so convoluted (like the scotch egg being a substantial meal thing).

I just think you have to be a pretty sad person to go to a crowded venue knowing that you have Covid (which would be the only reason to fake a test result unless you really can't take one for some reason), or to pretend that you have a mask exemption just so you can go and breathe your germs over everyone.