Back in 1990 I was several years into a PhD in neural networks, having fun, but not really making especially useful progress. I spent a lot of time trying to g

Back in 1990 I was several years into a PhD in neural networks, having fun, but not really making especially useful progress. I spent a lot of time trying to get some simulated bugs to learn to move around, find food, and generally learn how to be better bugs. To help me understand why my learning algorithms didn't work, I'd written a nice graphical user interface, and generally camped out on a lovely Sun workstation belonging to some defunct research project, at least whenever I got to it first. About that time, the Bank of England issued a new five pound note and made huge claims that it could not be scanned. Supposedly they had designed in loads of high detail textures that would show weird aliasing artifacts on the 300 dpi colour scanners that were state of the art at the time. Challenge accepted! The Sun workstation I camped out on just happened to be connected to a nice 1200 dpi monochrome scanner. I went to my friends at the university theatre and returned with a whole stack of different coloured gels from the theatre lights. Then I took a whole series of scans of a £5 note through the various coloured gels, and wrote software to combine multiple monochrome scans into a colour image and re-align all the layers properly. As a result, my screen background was a perfect image on a supposedly unscannable £5 note. Six months later, I ran out of funding for my PhD without very much to show for it, but didn't fancy joining the real world. There were two research projects needing people, and I very much liked the idea of one on surgical robotics for neurosurgery, but I guess that was too ambitious and didn't get funded in the end. The one remaining project was on multimedia conferencing. Now, as an undergrad I had avoided all the classes on networking as I thought they would be boring, so I was spectacularly unqualified to do research on networked multimedia, but I applied anyway as I didn't really have any alternatives left. Of course the first question at interview was ``So, what do you know about multimedia?''. The honest answer would have been that I didn't know much at all, but that didn't seem to be what the Professor was hoping to hear. I couldn't think of anything else to talk about, so I told him all about faking £5 notes. A couple of days later I was really surprised to get offered the job, and a decade or so later, it was me that became Professor of Networked Systems. All because I couldn't resist the challenge to copy a £5 note.