John Davidson became the reluctant poster boy for Tourette's Syndrome when he was just 16 years old.
The little known condition, previously described as "wild madness", caused him to spasm and jerk, swear uncontrollably and shout explicit sexual phrases.
In the 1989 documentary John's Not Mad, he cut a sad and lonely figure as the cameras followed him around his home town of Galashiels in the Scottish Borders.
"Tourette's is such an awful condition that most of the time I don't want to be the centre of attention," he says.
"I want to be able to walk down the street and not be noticed because I'm shouting or swearing."
