You must apply for a TEN if you want to hold a licensable activity at a premises not licensed for the purpose. You should apply for the licence ten clear working days before the proposed event.
If you apply by post you must also send copies of your application to:
The police and Environmental Protection Team have three working days to object. If there is an objection then there will be a hearing.
If you intend to host an event in a public park or similar space, please contact email@example.com with the details of the proposed event, including a plan showing the layout and boundary of the event area.
You can apply for a Late TEN but only in exceptional circumstances. If a late TEN is objected to then the event can not go ahead. Gov.uk gives guidance on activities that are deregulated and may not need a licence.
Gov.uk offers guidance on TENs.