"In Humanities based subjects it is very common for teachers to organise units into topics and chucks. We teach the knowledge, skills and understanding of a particular unit and then move onto the next, thinking we have done our job. However, if we don't revisit this then learners easily forget this information. By adding in Diagnostic questions from previous units learners are reminded of previously taught content and have to recall and apply their previous understandings. It keeps learners on their toes, reminding them not to forget about previous topics and that covering something just once or twice, doesn't necessary mean we have learnt it."