Tom is now 11. At home, his favourite way to relax is to devise maths exam papers complete with marking sheets. Last year for Christmas he asked his parents for the £125 registration fee to sit maths GCSE, an exam most children in Britain take at 16. He is currently working towards his maths A-level. Tom is an only child, and at first Chrissie, his mother, thought his love of numbers was normal. Gradually she realised it wasn't. She would take him to lectures about dark matter at the Royal Observatory in London and notice that there were no other children there. His teacher reported that