The story of how Boston mob boss Whitey Bulger met with the IRA and set up the arms-smuggling deal is detailed in a new book.

The explosive new book ‘Whitey Bulger: America's Most Wanted Gangster and the Manhunt That Brought Him to Justice, Boston Globe’ by  Boston Globe journalists Kevin Cullen and Shelley Murphy tells how Bulger's involvement with the IRA "took off" after he began working as an FBI informer.

The book states that before becoming an FBI "informant", Bulger had no dealings with the IRA. It says: "Up to that point, he had merely donated relatively small amounts of money to Noraid, the IRA's main support group in the US. But now that he had the FBI in his pocket, his involvement quickly intensified. It became more than giving cash, it became a hands-on thing.

Read More: Whitey Bulger's secret links to the IRA and gun running

"Whitey first sent a small consignment of weapons to the IRA, then prevailed upon a friendly FBI agent to acquire C4 explosives for them, according to Steve Flemmi (Bulger's associate who testified against him). Finally, in 1984, Whitey sanctioned and helped organise the biggest ever shipment of weapons from the US to the IRA.”

"He considered the mission his crowning achievement, an interlude of honour in his long criminal career. It was an audacious project, but one that was doomed to failure because of that bane of Irish revolutionaries, the informer."

After being on the run for 16 years Bulger was arrested in California in 2011 and faces trial in June on 19 murder and other charges.