On a warm spring day long ago, I was sent to Philadelphia on assignment.

My subject was crooner Al Martino — better known today as the man who played Johnny Fontane in the iconic Godfather saga.

Martino picked me up from the 30th Street train station in his Cadillac and told me his own sordid, Mafia-tinged tale.

It unfurled over hours of drinking at mobbed-up South Philly watering holes.

At one, I asked the bartender about the city’s hyper-violent former Mafia kingpin, Nicodermo “Little Nicky” Scarfo.

The beefy barkeep, chatty and friendly to that point, put his finger to lips, then to the side of his head indicating the diminutive Mob dictator was a whacko.

Scarfo — who died in prison Jan. 13 at 87 — still instilled fear in Philadelphia more than a decade after being jailed for murder, racketeering and other crimes too numerous to mention.

At his sentencing, federal prosecutors were scathing about the well-dressed killer.

“(Scarfo) is a remorseless and profoundly evil man,” a prosecutor told the judge. “His life has been committed to the Mafia and all the negative values it represents: Greed, viciousness, treachery, deceit, and contempt for the law.”

The Brooklyn-born gangster said when he was a kid that he was going to “lick the world.”

His model was the charismatic, often witty Al Capone, but the two men couldn’t have been more different.

“There was no sense of charisma; not even a hint of the old Mafia mystique,” Philadelphia Inquirer crime reporter George Anastasia wrote. “Scarfo was a bully with a gun.”

Scarfo’s maternal uncles introduced him to the Mafia life.

Hot-tempered and unpredictable, Scarfo soon fell afoul of Philly’s genial Mob chief, Angelo “The Gentle Don” Bruno, an old-school gangster. Benevolent, business-like and discrete, Bruno was more Don Corleone than Don Corleone.

Bruno’s consigliere wanted the pint-sized palooka Scarfo whacked. Instead, Bruno banished him to the dying resort town of Atlantic City, N.J. in 1964.

Scarfo was so out on the fringe of Mob action, he worked as a bartender and maintenance man to make ends meet.

Then, a miracle happened. Gambling was declared legal in Atlantic City in 1976 and suddenly Scarfo was the Mob’s man with a plan, skimming millions off unions, construction, gambling and other forms of vice.

At the same time, the long peace in Philadelphia was shattered when Angelo Bruno was murdered on March 21, 1980. Scarfo’s hands were clean in the hit, but after years in the minors, he was called up to the big leagues.

Bruno’s replacement was Philip “Chicken Man” Testa, who’d been a mentor to the fast-rising gangster and appointed his protege consigliere.

Testa’s reign would be brief, ’cause as Bruce Springsteen sang in his 1982 hit “Atlantic City,” “they blew up the Chicken Man in Philly last night.”

What followed was a gangland settling of accounts nearing Biblical proportions in the City of Brotherly Love.

In the two years after Testa was obliterated by a nail-packed bomb, Scarfo drenched the streets of Philly with buckets of blood. Ten top mobsters were slaughtered.

Many more minions were given one-way tickets to the morgue. Death toll: 25.

By 1984, the lowly bookie was king of Philly, wearing his hair slicked back and bespoke suits like a poor man’s Gordon Gekko.

As Scarfo and the Philly Mob raked buckets of dough out of Atlantic City, he ruled the city and South Jersey with mercurial brutality.

Scarfo had created an unbearable climate of paranoia — crushing even lifelong criminals.

Two mobsters feared they were marked for death and, in 1987, turned canary.

Scarfo was arrested getting off a plane in Atlantic City, returning from his South Florida mansion he called Casablanca South. That was January 1987 — he would never spend another day as a free man, narrowly escaping a trip to the electric chair.

One of the finks, Nicholas Caramandi, later told the Philadelphia Daily News why he ratted.

“He could turn on you in a second,” the former hitman said. “And once he did, forget about it. It was all over for you. You might as well go to China.”

Don Corleone would not have approved.