when i was doing GCSEs one boy took a joke book with him and once he finished the exam took it out and started reading it.
last year when i was invigilating, a boy doing A-level geography, sneaked in his exercise book and during the first half exam sat and did absoletely nothing at the beginning of the second exam, asked to go to the toilet, an invigiliator accompnaied him, he looked in the book came back and aced the exam within 20 mins, after reporting him to the teachers, they did a search and found his book and he got excluded from all exams