That's because although it is not illegal to photograph or film somebody in this country (no actual privacy laws), it doesn't mean that such evidence would be admissable in a court of law. That is up to the Judge to decide.

In some businesses or properties, it may not be permitted because of data protection laws.

Ultimately, anyone can appeal to the Human Rights court, but rather unlikely.

We are all filmed (without our permission) many times a day on CCTV cameras, both private and public.

Of course if you were found to have filmed somebody for voyeuristic reasons, then you'd no doubt be in trouble. It's the motive that matters.