A group of elderly men nicknamed the "Bad Grandpas" robbed an estimated $20 million in jewels from an underground deposit facility in London through some audacious means, a new book describes.

The eight men, who were experienced criminals, ages 52 to 73 at the time, concocted a bold plan while drinking at the pub to break into the Hatton Garden Safe Deposit in the diamond district of London in 2012. Three years later, after purchasing a diamond-tipped drill and a copy of "Forensics for Dummies," the men successfully burrowed into the safe on Easter weekend of 2015 and made off with millions in precious jewels packed into empty garbage bins.

“The Last Job: The ‘Bad Grandpas’ and the Hatton Garden Heist” by Dan Bilesfsky tells the story of the robbery and where it went wrong -- eventually leading to the gang's capture and conviction.

“This represented a final hurrah,” author Dan Bilefsky told The New York Post. “They were motivated by cash, but, at a time in life when many of their contemporaries lived in nursing homes, the excitement of a final heist got their hearts going.”

“They felt that they had nothing to lose," he continued. "There was a brazenness that was born of age.”

It all started when 73-year-old Brian Reader, nicknamed "The Guv'nor" began complaining to his friends that he needed some extra cash, although his home was valued at about $1 million at the time. He and his colleagues, who declared themselves as "The Firm," decided that the Hatton Garden Safe would be an ample target, as it housed about 1,000 security boxes full of valuable goods, including jewelry, cash and gold.

For the next three years, they devised their plan, purchasing a copy of "Forensics for Dummies" to read up on DNA testing techniques and a $5,200 drill to penetrate the vault's reinforced concrete wall. The crew watched YouTube videos to learn how to use the drill and reportedly practiced in the plumbing shop of one of its members, 47-year-old Hugh Doyle, which was overheard by some neighbors.

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On Easter weekend in 2015, Reader assembled his full team: Michael “Basil” Seed, 54; getaway driver John “Kenny” Collins, 74; “extra pairs of hands” Carl Wood, 58, and Terry Perkins, 66. After the heist, they enlisted William "Billy the Fish" Lincoln, 59, who helped them hide the stolen items.

Around 8:30 p.m. on the Thursday before Easter, the group destroyed the security cameras at Hatton Garden, shut off the alarms and spent hours drilling into the wall of the safe. Once they broke through, they discovered that the safety deposit boxes had steel sides, which they attempted to break with their battering ram, but broke the tool instead.

The men returned home, feeling discouraged, and the next day, the heist's leader, Reader, got cold feet. Carl Wood also changed his mind the next day and backed out. The rest of the group, however, persevered and were able to get into 70 of the steel safety deposit boxes and make off with the goods inside. They wiped down the crime scene with bleach to get rid of any fingerprints -- a tip they learned from their "Forensics for Dummies" book.

What they didn't account for, however, was the wide network of surveillance in London, and that one of The Firm members, Collins, drove his Mercedez-Benz to the crime scene, which is registered in his name, to act as the look-out.

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Police bugged the men's cars and overheard them bragging about their crime while trash-talking each other. About six weeks later, the men met to discuss how they were going to split up all of their goods at Perkins' daughter's house. It was there that police broke down the door and arrested all who were in attendance at the meeting.

They later apprehended Reader at his own home, and Wood, while getting out of his car.

Police then confiscated the stolen goods from various odd hiding places, including garages and under pots and pans -- one member even hid his jewels underneath the tombstone of his girlfriend's late father.

The men all pleaded guilty -- and seven members received seven years in prison for the heist. Doyle, however, received a suspended sentence.

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Perkins died from a heart attack while in prison in 2015, but the remainder of the men are still behind bars at the maximum-security facility Belmarsh prison, which also currently holds Julian Assange.

Despite their crimes, the public still had sympathy for the "Bad Grandpas."

“[The gang members] didn’t hurt anyone and there was a feeling of ‘good on them,’ ” Bilefsky said. “If they bore a hole through Belmarsh, that would be impressive. But I don’t think they will be escaping anytime soon.”