Welcome to part four of the surprisingly fruitful series of entries centred upon the curious individuals I find myself watching in the local library when I really should be writing.

No. 4: Dr Jekyll (and Missing Hyde)

Dr Jekyll is a middle-aged guy who comes in almost every day to read the newspapers and use the internet, who suffers from an intermittent but pronounced upper body tic.

Some days are noticeably worse than others, but on a typical day every few minutes he will suddenly and involuntarily arch his spine, throw his head back and twist his face into a rather alarming rictus, giving the distinct impression that he is about to transform into his evil alter ego. Fortunately Mr Hyde never fully emerges but the almost-transformation is very arresting indeed.

Most regular patrons of the library are well used to this sporadic display of corporeal fireworks but there's a guilty pleasure to be had in watching the reaction of an uninitiated newcomer who happens to sit next to Mr Jekyll at one of the computer terminals. Last week someone actually let out an involuntary scream.