This may or may not be asked of you. It will depend on the age group of the party or function, whether or not you have previously hired the hall, and other factors. Whether or not you do pay this amount (it is normally £65.00) you will still be liable for any damages caused whilst you are in the hall. Quoting from part of the Bookings Form:
SECTION (B) The returnable security deposit is your guarantee that you will leave the Hall in a reasonably clean condition, and may be used to cover any damages incurred during your period of hire. In each of the Halls available, there are notices reminding users of their obligations, and if necessary, you may be subject to additional costs, even if you have, or have not paid a returnable security deposit.
SECTION (C) IMPORTANT: As the hirer it is your responsibility to make sure your events are properly supervised and organised. Any damages that exceed your hire charge, security deposit paid or not paid, will be legally and fully recoverable. We wish your hire to go successfully, but you will be held fully accountable for losses and damages during your period of hire, without exception. These losses will also be subject to any administration charges that we incur.