Per Dick Ballard:
I get the impression from some sources that NOT
allowing one's pet cat to free roam is considered a form of abuse by
many in Britain.

Couple years back I saw a documentary about a guy who studied cats in
the UK.

His method was to recruit a number of cat owners who agreed to seal
anything their cat brought home in a plastic bag and freeze it until the
investigator came around periodically to collect and catalog them.

I can't recall the numbers, but he found that each made quite a dent in
the local small animal population.
--
Pete Cresswell