The names alone sound like hard-boiled protagonists from a vintage Raymond Chandler or James Ellroy novel. But Arthur ‘The Brain’ Rachel and Joseph ‘The Monk’ Scalise weren’t the creations of fiction writers. Forty years ago, these men were veteran members of the Chicago mafia. Their specialty was assassination but in early September 1980 their target was jewellery, namely, gems that had once belonged to the family of Winston Churchill and which were now housed in a jewellers in the heart of London.

The (literal) star of the show was the 45-carat, cushion-shaped Marlborough diamond, which had been recut into a starburst design and took pride of place in the window of Knightsbridge jewellers Graff. In today’s money, the stone would be worth in the region of £2 million.

Joseph, known as ‘The Monk’ due to a claim he made as a younger man that he would one day like to be a priest, along with Rachel, known as ‘The Brain’ due to his IQ score of 162, were the men tasked with carrying out an operation which, to this day, is believed to be the most valuable unsolved diamond heist in British history.

Before we get to that, however, it’s important to know the bizarre history that landed the diamond in the store window of Graff in the first place. It belonged to Gladys Deacon, the second wife of the Duke of Marlborough, Winston Churchill’s cousin. A noted intellectual and great beauty in her day, Deacon was admired by multiple luminaries including French novelist Marcel Proust, who declared, “I never saw a girl with such beauty, such magnificent intelligence, such goodness and charm.”

In an effort to maintain her legendary, captivating looks, Gladys subjected herself to an early, and horribly ineffectual, attempt at plastic surgery on her nose. Injecting paraffin wax, the operation grossly disfigured her. Becoming a recluse she was eventually institutionalised, spending the last 15 years of her life in a home before dying in 1977. It was only after her death that the stone was sold to Graff and reset as a necklace from a brooch.

It was this jewel, more than any other, which The Monk and The Brain had their eyes on. After flying into London from Illinois, the duo spent the next few days sizing up the jewellery store, which had a front door that was only unlocked to allow customers to enter once they had been screened by a security guard.

Rachel and Scalise had a simple plan to ensure that they would be granted access. Dressed up as Arab sheiks with fake beards, they hired a Fiat Mirafiori to drive to Sloane Street in Knightsbridge where the store was, and still is, located. It was broad daylight and five employers and two customers hit the floor as Scalise walked in brandishing a revolver and, entering behind him, Rachel showed what appeared to be a hand grenade.

Barely saying a word, the men went straight to the window display and started filling a briefcase. The owner of the shop, Laurence Graff, later said the thieves had clearly known what they were after: “They picked out the very special pieces from the window,” he said. “It was all over in less than a minute.” No-one was hurt during the raid and so smooth and quick was the operation that staff and customers on the upper two floors of the three-storey shop weren’t even aware it was happening.

But the seeds of the thieves’ downfall were already sown. An alert accountant who worked for Graff was returning from his lunchbreak when he noticed two men, one of whom appeared to be wearing a fake beard, taking off white gloves as they left the doorway of the store. Following the two men, the accountant noted the registration number of Scalise and Rachel’s car. He would later tell Scotland Yard that he was convinced by the sight of the men that there was “something rotten in the state of Denmark”, a line from Hamlet suggesting that things might not be exactly what they seem.

Understandably, the pair were keen to get back to the States as soon as possible. But this was where Rachel’s formidable IQ seems to have deserted him. Within hours of the robbery being reported, the police had traced the hire car as having been rented from Hertz at Heathrow airport. Incredibly, the duo had booked the car under their real names, as were their bookings at the hotel and their plane tickets back to Chicago. Their arrest by the FBI, as they alighted at O’Hare airport, was swift. Yet neither Scalise or Rachel had the diamonds on their persons.

The next few years would see an epic legal battle for extradition with both men eventually being recalled to the UK in July 1983, where they served almost a decade at HM Parkhurst on the Isle of Wight.

Incongruous as the reality of two Chicago mobsters languishing in a prison cell near Cowes and the River Solent was, answers from Scalise and Rachel about the whereabouts of the diamond were not forthcoming. A London cab driver told police that Scalise and Rachel were in his car on the day of the heist and asked him to locate a Post Office and post a parcel for them – which he did. A post office clerk, put under hypnosis by the police to assist his powers of recall, declared that he had handled a package later that day and that is was addressed to New York. He couldn’t, however, remember the specific address.

Could that package have contained the Marlborough diamond? Scalise’s sister lived in New York at the time but, despite investigations, the trail went cold. Years later, in 1999, an unnamed Chicago Mob associate of Scalise told FBI investigators that The Monk had indeed mailed the diamonds to his sister in the Big Apple immediately after the heist.

The duo themselves, although sloppy criminals, were a little more seasoned when it came to upholding the mafia’s omertà. While in jail on the Isle of Wight, FBI investigator Jack O’Rouke travelled across the Atlantic to dangle the carrot of a reduced sentence in front of the duo should they reveal the whereabouts of the Marlborough diamond. Both Scalise and Rachel refused point blank, with Rachel refusing to even leave his cell for the interview.

What does seem probable is that the duo benefitted little from the value of the diamond. As Scalise’s attorney, Vadim Glozman, drolly pointed out in one interview, “as far as I’m concerned if he had it he wouldn’t be living off social security benefits.”

Both The Monk and The Brain swiftly returned to lives of criminality after their eventual release and return to the States. One conviction was for an attempt to hijack an armoured van and rob the house of the widow of a former mob boss. At the time of writing, however, both men are free and living in Chicago halfway houses. Now in their early 80s, the two continue to deny knowing anything about the whereabouts of the Marlborough diamond. Interviewed in 2001 by the American ABC television network, Rachel stated that he’d already spent the money and, when asked how much he made from the diamond deal, retorted, “none of your business.”

As aging wise guys, the culture of a lifetime in the mob means the chances of authorities getting any clear answers remain slim. “It’s the way we are. We got nothing better to do,” was Rachel’s response when asked by a US district court judge why he continued his life of crime into such advanced years before his sentencing for the robbery attempt in 2012 (then aged 73). Federal prosecutor Amarjeet Bhachu was more scathing of Rachel, stating during the trial, “This thug has the gall to ask for leniency when he does the same thing over and over. He is a parasite. He lives off of others. The public needs to be protected from this man.”

If Scalise didn’t profit from the Marlborough diamond, he has certainly made some money from Hollywood. In recent years he has been employed as a consultant by director Michael Mann and on the Johnny Depp film Public Enemies.

The reward for the return of the stones still stands at $100,000. Though, as the men enter their twilight years, it seems increasingly likely that any carrot dangled in front of them simply won’t compete with their sacred code of honour. Writing to the weary FBI investigator O’Rouke from his Isle of Wight prison cell in the 1980s, Scalise quoted Nietzsche: ‘You have your way. I have my way. As for the right way, the correct way, and the only way, it does not exist.’

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