Under 2s go free when accompanied by an adult with a valid ticket.
All guests require a valid ticket to enter, most ticket types will offer the option to add an under 2 ticket either while selecting the number of Adults and Children, or after you have selected the date and time of your booking. These will be added to your basket prior to checkout.
If you are unable to book a ticket for your under 2 in advance please do not worry. If you talk to a member of staff upon your arrival, they will be able to issue an additional ticket for your little one.