It's not a Ball in the sense of a ballroom with a band and long dresses. It's mainly a more modern day prom like affair, but much bigger and a wilder! The Ball is set up over most of the grounds of the college - many marquee tents set up to house 2 stages of live music, many food stalls, games, and plenty of drink options. Recall that the drinking age is 18 here and Oxford is by no means a "dry campus". So any kind of drink is flowing all night long. The Ball is not cheap to attend, tickets were 80 GBP, which is $120 per person. It starts at 8pm and lasts until 4am.
We also went with one of Brian's physics colleagues Uwe who is also a Fellow, and his girlfriend Evette. I thought it might be a little weird if just Brian and I went and roamed around the students on our own. It was fun to get to know Uwe (German) and Evette (English) better - they were tons of fun. Unfortunately it was difficult to remember to get the camera out and it got dark quite quickly so we don't have many photos. But hopefully there will be some up on the Ball website.
Check out the Keble Ball website so you can get an idea of what it's all about.