When I first joined the police in the late 1970s computers were big things locked in rooms and operated by punch-cards. I had no chance of getting involved. But in the early 1980s I started messing about with Spectrum and Commodore 64 consoles at home and became completely obsessed.

I was trying to find ways to use computers in police work. I created a database for disqualified drivers for the Met and computerised templates for charge sheets. In the 1990s we started examining the computers of paedophiles. Then, in 2000, I heard the police were setting up a national hi-tech crime unit and looking for a head of forensics. I thought, “how perfect”.