Jimmy MacDonald was convinced that there was a conspiracy against him. It was led, he believed, by members of the Catholic Church who regularly got together in secret meetings and decided on new ways to punish him for the fact that his sister had got "in the family way" and deserted the church.
As a result of these secret meetings he'd received poor marks for his fifth form essays, been told that he was not intelligent enough to progress to the sixth form, and been excluded from the school's cadet force.
And if this wasn't enough proof of the conspiracy against him, then how about the fact - it was always a "fact" - that Brother Murphy, the headmaster of our school at that time, always walked straight past him rather than giving one of those affectionate nods which he bestowed on the other boys in his charge.
And how about the other "fact" that he was in the school"s second team for football even though his brother had once had a trial for Everton.
And how about the other "fact" that a car had driven straight at him last Thursday when he was crossing the road to buy some sweets at the Endbutt Stores.
We did occasionally try to argue Jimmy out of his conspiracy theory, to point out that his essays were not of the highest standard, that lots of other boys had never made it to the sixth form, that people who were below average height (MacDonald only came up to my shoulder) were rarely recruited to the cadet force, that Brother Murphy only smiled at the younger prettier boys in the school, that his brother's prowess at football was no guarantee of his own ability, that people were always having narrow escapes when they dodged through traffic to get to the Endbutt Stores.
But to tell the cruel truth we devoted considerably more time to feeding his paranoia.
We routinely stole text books from inside his desk, moved his satchel around the classroom, failed to pass the ball to him during playground games, and, on occasions jammed a lock so that he was imprisoned in a toilet cubicle for the whole of a lesson.
Conspiracy theories are greedy animals.
They swallow every titbit that is lobbed their way. So perhaps it was not too surprising that by the time Jimmy left school he was in possession of a belief system which was totally at odds with reality. It was a belief system which led him to marry his sweetheart Jean in almost total secrecy in case the Catholics found out about his plans and refused him the sacrament.
And it was the same paranoia which led him eventually to join the police force. When he told us about his decision one night in the Legs of Man pub, he said at first that he'd joined up because of the free housing provided by the force. But only moments later he'd added the information that once he was in the force he'd not only be safe from further persecution by the Church but could also investigate some of its sinister practices.
I lost touch with him during his days in the force but about five years later I accidentally met up with Vinnie, his footballing brother.
"Is Jimmy all right these days?" I asked carefully. "Not really", said Vinnie. "They asked him to leave the force." "Any particular reason?" "Well, apparently he got some bee in his bonnet about how the Catholics were running the local crime scene."
"Doesn't sound enough to get him sacked." I said sympathetically.
"No, I agree" said Vinnie. "But as I've heard it, matters came to a head when he arrested the parish priest."
"On what grounds?"
"Well, according to Jimmy, he was a leading member of the conspiracy and had personally tried to get Jimmy off his back by giving him a poisoned communion wafer."
"It sounds as though he really flipped."
"Yep" said Vinnie philosophically "And he's now lost his job and his house and believes it's all down to the Catholics."
"Was he always a bit on the paranoid side?" I asked gently.
"Not really" said Vinnie. "He only got really bad when he started having all those delusions at school."
"Yes. He somehow got it into his head that someone was stealing his books and moving his satchel and even locking him in the lavatory."
Conspiracy and paranoia. They'll be up for discussion when I meet the author of a new book on the global phenomenon of conspiracy theories.
That's at four o'clock today or after the midnight news on Sunday or on our podcast.
Also on the programme: what determines our reaction to the suffering of strangers?
Laurie Taylor presents Thinking Allowed
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