Pace Sky digibox User Manual page 26

Regardless of your Parental Control settings, you'll need your PIN to
watch any Box Office programme shown before its normal watershed
time. PINs will be required as follows:
Programme rating
If you order a Box Office programme using your remote control but
then do not tune to the relevant channel at any time during the
programme, you will not be charged for it.
Your Sky digibox must be connected to a phone line in order for you
to order movies and events etc. using your remote control.
22
When PIN is required
18 programme starts before 10.00 pm
15 programme starts before 8.00 pm
12 programme starts before 8.00 pm
Using your Sky digibox