Apparently, a fire alarm went off in my DS's maths exam. They didn't have to evacuate as they established it was because of someone burning something in the kitchen (my interpretation of why 'opening an oven door' would have triggered a smoke alarm!) but they had to stop the exam for nearly 20 minutes and the students had to sit in silence.
I got this from the school, not DS himself.
Special consideration is being applied for for the whole year group!