The Access Code says:
Access rights can be exercised in most urban parks, country parks and other managed open spaces. These parks are normally provided for recreational and educational purposes, but may also be managed to help safeguard the environment. Where the levels or types of use are such that peoples' safety or the environment is at risk, local guidance or management measures, such as management rules, regulations or byelaws, might have been introduced. Follow such guidance to help ensure that safety or the environment is not put at risk.