A day ticket is needed for admission to all events on site. If you;re going to the evening concert in the barn you need a ticket, but they sold out ages ago (they go very quickly); similarly you need a ticket for the buffet meal in between afternoon events and the evening concert in the barn. If not going to the concert, there is a session, again in the Royal William, for those who want to go (no tickets needed). I think there were still day tickets available at the moment, judging from the conversation I had with the office this morning.