Twenty-one or over, the guest and anyone else present
Every guest, and everyone else present in the room, must be twenty-one or over, and she may ask to see a photo document at the door before anything starts.
The age rule on this site is twenty-one or over, with no exceptions. It applies to the guest who books, to a partner in a couples booking, and to anyone else who is in the room when she arrives. The site itself asks visitors to confirm the same age before they read it.
At the door
She may ask to see a photo document, such as a passport or a national identity card. She glances at it, returns it at once, and keeps no copy, photo or written record of it. If she cannot be sure that everyone present is twenty-one or over, she leaves before anything starts.
Why it matters after an evening out
A booking made on the way back from a bar or a club is where this rule is tested. Friends from the evening who come back to the room for a last drink, a younger member of a group who tagged along, a new acquaintance from the square: none of them can be there when she arrives. The booking is for the guest or the couple who made it, everyone present must be twenty-one or over and part of the arrangement, and anyone else needs to have left before she knocks.
What it costs if it is not met
A visit that does not go ahead because the rule was not met is treated as ended by the guest. The age statement sets out the rule in full, and the page about leaving the group behind covers the practical side of heading back alone.