Shaved head, scarred, and tattooed, it all added to the hardman look of the former boxer and security firm boss as he swaggered the streets.
Far from the big city lights of England where he gained a fearsome reputation as a gangster, the 45-year-old died in an accidental fall at his isolated home on a hillside in Durrus, near Bantry, Co Cork, on Tuesday.
His 23-year-old girlfriend Siobhán Ginty, who Isaac said he planned to marry, had returned to England only last week. She is due in Cork tomorrow, most likely to bring the remains back to Britain for burial.
Yesterday, in villages and towns where Isaac, at 6ft 4in was easily spotted, usually on market days, it was difficult to find someone to say a kind word about him.
“I often saw him around, never addressed him, one look at him was enough to keep out of his way,” said a villager in Durrus.
“To be honest, most people never really got to know him but his burly looks and threatening presence was enough for people to keep their distance.
“He may have been a nice guy and I saw in the papers where he said he came here to live a new life. For that reason, I would feel sorry for him if he planned to be crime-free.”
Others, however, claimed Durrus became a “garrison town” as gardaí made more visits than normal when Isaac was resident at his home, named Ratsville.
“There was one bank holiday when the village was jammed and there wasn’t a drink to be served, a minute after closing time, as the place was swarming with many gardaí, including Special Branch,” one local claimed.
“And the reason for it was they kept a close eye on Isaac and his friends.”
A businessman in Bantry, like all others, did not wish to be named. “Nobody knows who his friends or enemies were,” he said.
“He did no harm to me. I did shake his hand a few weeks ago, out of politeness.”
Isaac was released on a large cash bail last month at Bantry District Court after being handed a five-month jail sentence for his role in the assault of a waitress in Durrus last April.
The case was due to be heard in a circuit court appeal in December.
In court, he had described life in Britain as “being crazy over there” and, in evidence before Judge James McNulty, said he planned to start a new life here.
A British friend and boxing gym manager, Bob Shannon, once described Isaac as a genuine, caring, person.
“Don’t take the book by its cover... of course Billy’s a very hard lad, but he’s got another side to him,” said Mr Shannon who, after his son’s death in a car crash, was comforted by Isaac.
That “other side” of Isaac was rare, it appears. Media in Manchester, where Isaac was born, and in London, where Isaac was regarded as a lieutenant to a notorious crime family, had nicknamed the ex-professional heavyweight “bullet man”.
Boxing legend Ricky Hatton said during a court trial for Isaac that he was “a great inspiration and used to help my training sessions”.
He claimed that Isaac “helped local youngsters to get off the streets and into shape. He also taught them to be respectful to others.”
Isaac’s thuggery in the Durrus assault, however, was noted by the sitting judge, who dismissed him as a bullyboy.