James 'Whitey' Bulger is said to have stolen masterpieces worth £385million in the biggest art heist of all time but also the largest single theft of private property in America.

Despite a $10million (£7.7million) reward, none of the works have been seen in public again as a blank frame sits on green silk wallpaper in the Isabella Stewart Gardner Museum in Boston.

The Concert, a masterpiece by Johannes Vermeer is now the world's most valuable missing work of art, with an estimated worth of $200m (£154million) went missing.

An empty frame hangs on green silk wallpaper in the Isabella Stewart Gardner Museum in Boston after the biggest art heist of all time took place there in 1990

Christ in a Storm on the Sea of Galilee, Rembrandt's only known seascape also disappeared.

Like the Vermeer, it was cut from its frame in 1990 and disappeared, along with two other Rembrandts, five Degas sketches, a Manet painting, a landscape by Govert Flinck and a bronze finial from a Napoleonic battle flag.

In all, around half a billion dollars worth of art.

The theft, in the early hours of 18 March was executed by two men dressed as police officers who, after handcuffing museum guards, spent an almost leisurely 81 minutes in the galleries - Bulger's name has always been associated with the heist.

The former mob boss was killed in prison last week while serving two life sentences for 11 murders.

From the early 1970s, Bulger headed the Winter Hill Gang, an Irish-American mob that terrorised Boston for more than a decade. But he lived a double life as an FBI informant, feeding the bureau information about rival criminals.

After going on the run in 1995, Bulger spent 16 years on the FBI's most wanted list, topping it briefly after Osama bin Laden's death in 2011.

The Concert, a masterpiece by Johannes Vermeer (pictured) is now the world's most valuable missing work of art, with an estimated worth of $200m (£154million) went missing

Later that year he was arrested while living in a seafront apartment in Santa Monica with his longtime partner Catherine Greig.

The elderly couple had been hiding in plain sight and were known to neighbours as 'the Gaskos'.

FBI agents found a stash of $800,000 (£616,000) and an arsenal of 30 firearms.

However, art lovers were left disappointed when a Vermeer wasn't found above the bed or a Rembrandt in the sitting room.

After his arrest, Bulger did not volunteer information about the Gardner heist that might have brought a more lenient sentence or a more comfortable cell.

Christ in a Storm on the Sea of Galilee, Rembrandt's only known seascape also disappeared

And yet, according to Charles Hill, a former Scotland Yard detective turned private investigator, Bulger was the key to the theft.

'On the new morning of 18 March 1990, even the dogs in the streets of south Boston must have known that Whitey was involved in some way before, during, or after the robbery,' Hill told The Observer.

'Whitey was an IRA sympathiser, he loved to associated himself with 'the cause', and was involved in arms deals and drugs shipments to the Republic.'

Bulger, who was an IRA sympathiser, is believed to have given the artwork to the IRA

Hill believes the paintings were shipped to Ireland as part of a deal with an IRA-affiliated gang.

'After a shipment of weapons and ammunition was intercepted by the Irish navy off the coast of County Kerry in 1984, Whitey felt he owed one to his friends in the Republic. I believe he offered them the paintings.

However, there is no hard evidence for this.

Hill has been an undercover detective, he has led the 1996 operation to recover Edvard Munch's The Scream, stolen two years earlier from the National Museum of Norway.

In 1993 he led the recovery of a Vermeer and a Goya stolen in 1986 from Russborough House in County Wicklow, a theft was masterminded by Martin Cahill, a Dublin gangster known as the General, a nickname which gave title to the 1998 John Boorman film in which Brendan Gleeson played the crime boss.

According to Hill, the latter heist – with the Vermeer being the prize asset – was the inspiration for the Boston job.