Kids Go Free vouchers mean that you get one child ticket for free if you buy a standard full price adult ticket. A standard adult ticket is currently £50.
Unless otherwise stated on your voucher, this can only be redeemed at the entrance gate on the day of your visit, and is not valid with any other offer, on premium tickets or on free tickets. The expiry date will be listed on your voucher – after this date has passed, you will no longer be able to use this voucher.
We hope this answers your question.