I worked for the Mafia and these are the biggest secrets I've had to keep

With a million dollar smile he admits killing at least two people, shooting several others and laundering billions
of illicit dollars for the Mafia. He was Marilyn Monroe's lover, and counted Elvis Presley, Frank Sinatra and Marlon Brando among his friends. So it is little wonder that when director Martin Scorsese was casting The Godfather, widely considered one of the greatest films ever made, he chose charismatic real-life mobster Gianni Russo to
play the Mafia don's wife-beating son-in-law Carlo - after the mob made the film's producers an offer they couldn't refuse.

"Either the kid gets the part or you'll be shooting your ****ing movie on the moon," mob boss Joe Colombo warned Paramount Pictures executive Robert Evans.

Russo, who claims to know the secret behind the assassination of President John F Kennedy, why Monroe was in fact
murdered, and where union leader Jimmy Hoffa's corpse can be found, is poised to reveal all in his new memoir - Mafia Secrets - coming out in November.

"Being cast in The Godfather completely changed my life," says New Yorker Russo, aged 81, who went on to appear in many movies and even launched a singing career while still working for the mob.

"I understood the world in which The Godfather took place. I was clearly right for that movie."

But Sinatra begged Russo not to appear in the film, anguished that its portrayal of a singer whose career was aided by the
mob - along with the judicious placement of a severed horse's head - was based on the Rat Pack crooner.

"He called me and asked me 'as a friend' to quit the movie," recalls Russo.

"I asked him if 'as a friend' he'd have turned down his Oscar-winning role in From Here To Eternity if I'd asked him.

"He hung up on me."

James Caan, who played the Godfather's volatile heir Sonny Corleone, resented Russo muscling in on the 1972 movie classic.

"He could be a jerk. When we filmed the scene where Sonny beats up Carlo, he really kicked the **** out of me. He beat me with a trash can, and kicked me so hard I went airborne and broke two ribs.

"Brando didn't like the idea of a non-actor being in the movie and tried to get me fired. I pulled Brando aside and said: 'Listen to me closely, you get me fired, I'll **** on your heart. I will bleed you out here today'.

"He said, 'That was brilliant!' He thought I was acting. After that we became good friends, and he gave me acting lessons, running my lines with me every day. I stayed friends with Sinatra, and he gave me singing lessons. I learned from the best."

The Godfather launched Russo's Hollywood career.

Soon he was dating Liza Minnelli, appearing in murder mystery Have Gun, Will Travel, and with Brando again in The Freshman. But he continued working for the Mafia, which had its hazards.

"I've been run over by a car, stabbed, shot several times, and had my throat slit requiring 84 stitches," he reveals. Mob ties run in his blood. His great-uncle was a Sicilian Mafia boss hanged for mass murder.

Russo killed his first man at the age of 12: "I contracted polio at the age of seven and spent five years in hospital, where an orderly was a notorious paedophile molesting boys on the ward.

"I sharpened a broom handle into a shiv for protection, and one night when the orderly came for me I stabbed him in the heart. They put me in the psych ward for 72 hours, but finally decided it was self-defence."

Released from hospital soon after, the 12-year-old Russo was taken under the wing of Mafia boss Frank Costello, impressed by the juvenile killer. Russo ran secret messages to other Mafia bosses across America, becoming a trusted courier, eventually transporting millions in mob earnings. Mob work made him a millionaire by 16, living the high life.

"I was 15 and Marilyn Monroe was 31 when we became lovers," he says. "I was a good looking kid and she took a fancy to me. She invited me to her suite at the Waldorf, dropped her robe, slipped into the bathtub and said, 'Get into the tub with
me'. We made love all weekend and on Monday I could barely walk. After that we stayed friends until her death."

Russo also grew close to President Kennedy thanks to his mob connections.

"At a Las Vegas party I saw JFK snorting cocaine off actress Juliet Prowse's stomach," Russo recalls.

"The mob had helped patriarch Joe Kennedy become a millionaire bootlegger during Prohibition, and Joe had the mob pressure trade unions to help elect JFK president - on the promise that Kennedy would invade Cuba and return the mob's casinos that Fidel Castro had seized.

"But after the Bay of Pigs invasion failed, mob boss Frank Costello warned Joe Kennedy, 'You don't get Castro out of Havana, we start taking out your sons'."

The Mafia plotted to blackmail the president by secretly filming a three-way sex romp with FJK, his brother Robert, and Marilyn Monroe, claims Russo."But Sinatra tipped off Monroe that she was being set up, and she went ballistic, threatening to tell the world that RFK had made her pregnant and she had an abortion.

"A week later she was dead - murdered by an injection of air in her pubic region - on RFK's orders, I was told."

JFK's failure to recover the mob's lost Cuban casinos sealed his fate, says Russo.

"I was sent to deliver a message from Frank Costello to the heads of all the other Mafia families: 'It's on!'

"Every family had a gunman in Dallas that day in November 1963, but it was mobster Johnny Roselli who claimed to make the fatal shot from a storm drain."

One of America's most enduring crime mysteries is the fate of powerful union leader Jimmy Hoffa, missing since his abduction in 1975. "He was killed and left inside a Buick that was crushed into a 3ft metal cube, which a mobster now uses as the base for a glass table in his Florida home," says Russo.

He went on to own a Las Vegas nightclub, which is where he killed his second man: a patron beating up a woman with a broken champagne bottle. "I ran to stop him and he slashed my neck open. I pulled a gold-plated .25 from my pocket and shot him in the forehead.

"The police called it justifiable homicide, but he turned out to be a drug dealer for Colombian drug lord Pablo Escobar.

"Before the cartel could kill me and my kids I flew to Colombia to explain to Escobar. I was beaten and tortured, but then Escobar appeared and said, 'Why didn't you tell me you were Carlo in The Godfather? I love that movie.'

"He had me cleaned up, brought to his home and asked me to act out my closing scene in The Godfather, with Escobar playing Michael Corleone. When the scene was over he had me flown home and promised, 'I'll straighten everything out.'"

Russo even struck a deal to launder drug money for Escobar, "which made me a mint", he laughs.

He also alleges to have laundered a fortune in Mafia funds for the Vatican. "Over 15 years, $300million in cash went from Vegas to the Vatican," he claims. The Vatican has previously faced reports of money laundering and illegal bank transfers, something it denies.

Russo also claims to have moved illicit money for Pope Paul VI. But when Pope John Paul I ordered the money laundering to stop, he died just 33 days after his election. "He was killed for not getting with the programme," claims Russo. "Once Pope John Paul II was elected, the deliveries began again, and the Pope gave me six original Michelangelo sketches by way of thanks."

Russo now has 14 children and 23 grandchildren, runs his own charity giving scholarships to underprivileged children, and at 81 continues to sing in nightclubs.

"No way I'm retiring," he says. "I'm in negotiations to turn Mafia Secrets into an eight-hour TV series and I'm writing my next book on celebrities and gangsters. I have no regrets. I'd do it all again."

Mafia Secrets by Gianni Russo (Citadel Press, £25.99) is published on November 25