The central government can introduce laws and policies that would affect the work of agencies. For example, in April 2019 the Home Office made it easier for the police to stop and search anyone for an offensive weapon without first having reasonable suspicion. This power comes under section 60 of the Criminal Justice and Public Order Act 1994.
The serious violence strategy (example of national policy)
Gives the police more powers. This aims to involve other agencies such as youth services, the NHS, social services and education. (e.g. children excluded from schools are vulnerable to county lines which are a major factor of violent offences).
Some of local policies are set by the Home Office but others are set locally. For example, in areas where knife crime is high, police may respond with measures such as increased stop and search.
From time to time local polcies forces hold weapon amnesties where they would not arrest people who surrender illegal weapons. For example, a 2 week gun amnesty in London in 2017 led to 350 firearms and 40.000 rounds of ammunition being handed in. Amnesties aim to reduce the criminal use of weapons in the area.
On national and local level, the priorities of agencies can be affected by media coverage of a particular crime. The moral panic in press about "dangerous dogs" led to the introduction of a law that was ineffective in protecting the public. Sometimes police de-prioritise offence where they feel it's too trivial and a waste of ppolice resources or too difficult ot enforce the law.