That's partly @BorisJohnson's fault: his speech said something along these lines (right).
But it's harmful to suggest to people that these tests are the law. To do so restricts their liberty more than the law does.
The purpose of the legislation is to stop the virus spreading, by stopping unnecessary inter-household contact.
Baffled by reports some police have tried to stop sale of EEs altogether (have they really?!). Adding an EE to your grocery shop obviously creates no public health risk.
- Law-abiding people are told the legal restrictions go further than they do and so are deterred from lawful/harmless activity
- Some bad judgement reduces public trust in, and respect for, police.
Couldn't both members of the public, and the police, just do that?