the authorities work with their hands tied behind their back thanks to legislation, most of which hails from the eu, which gives the suspects more powers than the police.
that, and of course political correctness and a fear of offending "communities"
e.g. rotherham, rochdale etc.
ask most muslims, and they will laugh at the way british and european society has made it so easy for those muslims who wish to, to take advantage of the system and how afraid we are in challenging them, how easy it is to circumvent immigration law, how there is no pressure to learn the language or integrate, how everything is done to promote diversity rather than integration. toughen up they say, stop being such wimps. take control of your society before they do.