It's a very niche academic area, but it is fairly well represented, up through to the very highest quality research institutions - LSE and Cambridge both have Criminology departments/research groups, and while they aren't the largest ones there, they do exist. Cambridge is actually introducing a Criminology specialization in their Human, Social, and Political Sciences course (which is also notable as you can study Psychology as an option in first year, and Politics and Sociology throughout, on that course).
However it's not necessary to study that in order to join the police - in fact no specific degree is required.