My mate was a DoS. One of the teachers was quite a nice bloke and a good teacher, with a DELTA and all that, but he had a bit of drink problem. One morning during the break and after a violent coughing fit he said "I'm sorry, you're going to have to let me go for the day - can you cover my class?" So my mate said, "Aren't you well?" He said, "Not too bad, but, er, see, I've just shat myself."