My trousers!

Naomi's giggling was all the answer I needed.

"Well, you saw my underwear!" she teased, "Is that Donald Duck?"

As I felt the ragged edges where a moment ago there had been a whole seam over my trouser seat, I remembered that I was, indeed, wearing bright yellow boxers with images of Donald Duck on them.

"What am I going to do?" I stood up, turning, "I can't spend the day with a big split in my trousers!"

"Hmm... I could lend you my PE shorts." Naomi suggested.

"Not funny."

"It's a little bit funny. Maybe you can find something to wear in lost property, but you don't really have time before..." Naomi was cut off as, just as she was saying, a bell rang out to announce the start of lessons.