I'm a year younger than Martin as well. I've never quite figured out our schooling timetables. Eg if he had more years with Lower and Upper Sixth than me in Scotland. But yup, I was 17 I think when I started at St Andrews, that or only just turned 18. Martin was 18 going on imminently 19. Which meant that I was just 22 when I started the PhD, whereas Martin started his a year later aged 24.