This was the question asked by Queen Elizabeth’s Grammar School, Lancashire, and here is my answer.
If you’d like to ask a question, do! The guidelines are on my contact page here. Or you can just put the question beneath this post. I can’t promise to answer every question as a video, as it’s very time-consuming, but I will answer either by video, audio or blog – and your school will get a mention here and on Twitter and my FB page.