I can honestly state that there was nothing dodgy on the computer whatsoever when I left-
I'm not accusing you of anything but there is something you need to consider. If there had been anything on the computer that (in their view) should not have been there, and you deleted it before leaving, there are still plenty of traces of it that the IT guys can find. Could you find yourself in such a situation?
Or did you mean that there has NEVER been anything dodgy on your computer?
Hopefully it's the latter.