For the last 20 years or so the jig-dancing, kilt-and-green-knickers-wearing priest has pulled publicity stunts that have made us a laughing stock in Britain, Europe and beyond.
Ah well, they said, he's Irish. That explains it.
Meanwhile, the little priesteen, as his grandmother used to call him, was getting away with behaviour that disgraced us all by association and should never have been tolerated with such mild repercussions.
His first caper was running on to the track at Silverstone in 2003 in a near fatal attempt to disrupt the British Grand Prix (and anyone who thinks that's funny should read what the drivers have to say about the numbers who could have been killed).
Then there was his infamous rugby tackle on a Brazilian athlete in the marathon at the 2004 Olympics in Athens, a cruel and irreversible action which destroyed the runner's best chance of winning a gold medal.
Again, anything but funny.
Yet once again, this was greeted by the global TV audience with an appalled hilarity, because he was an Irish priest and he dressed like a leprechaun.
Even worse, he again got away with only a mild rap on the knuckles.
Reading Aidan O'Connor's book, one feels that if the authorities had been less tolerant he might have been slower to wreak the kind of havoc he did.
The Germans got it right when they heard Horan intended to pull off another stunt at the 2006 World Cup finals in Berlin by unveiling posters praising Hitler while doing his jig.
His feet had barely touched the airport tarmac when he was lifted; he spent the next nine weeks in a tough jail and was then put on a plane back to where he came from.
His posters, one of which read "Hitler was Raised up by Christ to Punish the Jews", were confiscated. He admits himself that this changed his thinking on publicity stunts.
All this is detailed in O'Connor's intriguing book, which takes the reader far beyond the loopy leprechaun image. Does Horan deserve a biography like this?
Definitely not, and the less attention he gets, the better. But the book does serve a purpose in that it explains the beliefs that have driven him.
It turns out that he's not just barmy; there's a mad logic to his behaviour.
The early part of "Neilie's" life reveals him as a little boy with serious problems, unable to cope with school life.
Part of a large farming family in Kerry, his parents went to great lengths to help the cuckoo in the nest, switching his schools when necessary and generally indulging him.
He made it into Clonliffe College and found it so difficult to mix with his fellow clerical students that he was sent to a psychiatrist.
So his grasp on reality was always fragile. No sooner had he arrived in his first parish in London as a young priest than he wandered into a meeting of a weird Christian sect in a local Masonic hall and was deeply impressed.
So much for his years of education in Catholic Ireland!
Within weeks of being free in London he had taken on board a whole new set of beliefs: the Second Coming of Christ is imminent, He will rule the world from Jerusalem for a thousand years, Armageddon is around the corner, and all this is in the Bible if you know how to read it.
While all this was festering in his feverish brain, he went on being a priest.
But his preaching began to betray him and what followed bordered on complete breakdown.
Throughout the subsequent years, his family, the Catholic Church and the British authorities treated him with remarkable tolerance and kindness, endlessly giving him chances to get back on track.
But of course he knew better. And he was willing to do anything to highlight his message.
One can dismiss him as simply crazy.
But reading the book, one gets the impression that some of Horan's craziness is a kind of preening self-indulgence, possibly the result of being mollycoddled by everyone around him from childhood into adulthood and ever since.
There is also the disturbing episode which led to his three-day trial at the Old Bailey in 2004 for gross indecency with a child, which gets a chapter in the book.
Horan was found not guilty, but he admitted that he had been naked in the living room of his home in London during a visit by a female parishioner who had a fixation on him.
The woman had her daughter with her, who was then around eight years old, and the daughter claimed that she had been handling Horan's penis while he lay on the floor.
Horan said he was naked from the waist down because he had been applying cream to an itch and denied the child had touched him.
At the very least it appeared to be an unsavoury situation, although, after the not guilty verdict, Horan said it showed how careful priests have to be.
He is getting less attention these days and has been defrocked -- but not dekilted!
He is still convinced the Second Coming is imminent and in the meantime, as the book says, he dances and waits.
SIC: II