George Kimball America at LargeNot long after his premature retirement from the ring half a century ago, Roger Donoghue served as Marlon Brando's boxing instructor for On The Waterfront, in which Brando would portray a washed-up pug called Terry Malloy.

On the set one day, the screenwriter, Budd Schulberg, asked Roger if he could have been a champion had he pursued his pro career. "Well," Donoghue replied after giving the matter some thought. "I could have been a contender."

Incorporated into Schulberg's Academy Award-winning script, "I could have been a contender" not only became the most memorable line of the film, but arguably the most famous of Brando's career.

In the late 1960s, at the old Lion's Head in Greenwich Village, the patrons used to look forward to Donoghue's visits with much the same sense of anticipation as the denizens of Harry Hope's saloon awaited the arrival of Hickey in The Iceman Cometh. Roger had by then become a beer salesman, and when he dropped in a couple of times a month to monitor the supply of Rheingold and McSorley's Ale, he could be counted upon to buy a round for the house.

These visits would often last an hour or more, and while his audience often included prominent novelists, folk-singers, actors and newspapermen, Roger would be the centre of attention, regaling the clientele with tales from the worlds of theatre and boxing, often punctuated by animated shadow-boxing.

Although he had been a successful welterweight in his day, he rarely spoke of his career. I eventually learned why.

The son of an Irish immigrant cab driver in Yonkers, Donoghue had turned pro at 18, and by 1951 had won 25 of his first 27 fights when he was matched against Georgie Flores in a featured bout on the Kid Gavilan-Billy Graham card at Madison Square Garden.

Donoghue scored an eighth-round knockout in his Garden debut, but Flores was taken to hospital on a stretcher and died without regaining consciousness.

Roger donated his entire $1,500 purse from the bout to Flores' family, and while he boxed a few more times, his heart was no longer in it. He lost two of his last three fights and retired at the age of 21.

Although he rarely spoke of it, he was haunted by the episode for the rest of his life. In a 1979 New York Times interview, he related the tale of being approached by a youngster who said, "You killed a man. I'm going to tell everybody."

"You don't have to tell everybody," Roger replied softly. "They already know."

After On The Waterfront, Donoghue served for some time as Brando's minder, but he was less successful at keeping "Buddy" - as he would invariably refer to the actor - out of trouble than he had been in turning him into a credible middleweight.

Years later, when Brando was filming the original Godfather, Roger would cash in an old marker, scoring a plug for his company: in the memorable scene in which James Caan, as Sonny Corleone, beats the piss out of his brother-in-law Carlo, a Rheingold beer truck is prominently parked in the camera shot.

He also taught James Dean to box. Dean was going to play Roger in a film based on Donoghue's life, but the project died with Dean in that 1955 car crash.

A ringside fixture at New York fights, Donoghue became a bon vivant who moved easily between the worlds of pugilism, the arts and New York saloon society. He rarely missed a Broadway opening, seemed to know every actor in town and wrote a musical himself. Schulberg was a lifelong friend, and it was Norman Mailer who introduced him to his wife, the painter Fay Moore.

I hadn't seen Roger since the Lion's Head went out of business a decade ago, but last year his name came up in a conversation with the boxing editor and broadcaster Steve Farhood.

Steve had set aside one evening a month to visit a home for senior citizens on the Lower East Side, where he would show old fight films for the residents.

To his surprise, Farhood related, he had learned that one of the residents was a former professional welterweight named Roger Donoghue. I filled him in on what I knew of Donoghue's story, asked that I be remembered, and promised to drop by for a visit sometime.

"He may or may not remember you at all," warned Farhood. "He has Alzheimer's Disease. Sometimes he doesn't remember much."

The next time I ran into Farhood, I asked if he had mentioned me to Roger.

"He's not there any more," he replied. "He was deteriorating so rapidly that he had to be moved to an assisted-living facility in Brooklyn."

It was there that Roger died, at 75, last week. Somewhat infuriatingly, the obituary in his hometown Westchester newspaper began with the words "Roger Donoghue, the former boxer from Yonkers who killed a man in the ring in 1951 . . ."