Our ticketing partner, Eventbrite, uses a waiting list system which kicks in when an event sells out. When you're on the waiting list, you'll be notified if any tickets become available to purchase, either through cancellations or by us taking the decision to increase capacity for an event.
The waiting list works sequentially, so when tickets become available, they'll be offered first to the first person who joined the waiting list, then the second, then the third, and so on. It's always worth jumping on if you missed out on tickets - you never know!