In the United Kingdom, local authorities will first need to approve any application for an event to which the public is admitted. No approval, no event. The first priority must be to arrange insurance cover and details can be obtained from your local authority. An added complication is a whole new raft of legislation concerning Health & Safety in particular Corporate Manslaughter, which can involve the event organiser being charged with a criminal offence if any of the insurances and risk assessments are not fully completed well in advance of the event. If this very basic step isn't completed then any further activity should be halted until it is.