If it's the same as last year, which Andy and Neal did have a go at, here's what happens...
A somewhat attractive (according to Neal anyway) "elf" with a big nose approaches you and bugs you for half an hour to get you to sign up.
Once you sign up they take you into the basement of the venue for about an hour where you have fun and frollicks with said "elf" completing a series of tasks etc.
I'm not a fan of LARP (Live Action Role Play) but Neal and Andy both said they enjoyed it, so I'm sure if your into D&D it would be worth a look.
Can't remember the exact price but I think Neal said it was about £7.
As a side note i say "elf" in such a way because, as with all LARP'er types, our "elf" is actually just a run of the mill person!
Shattering news I know but some one had to tell you, lest you think it was a real elf!
Hope that helps!