The Hatton Garden ringleader, known as "Basil," was found guilty four years after executing the £ 14 million raid.
It is assumed that the alarm specialist Michael Seed, 58, with a key set before the deactivation of the security system in the locking system in London has taken.
He was one of two men who had climbed into the vault to plunder 73 lockers after a group of criminals had drilled on a thick concrete wall during the 2015 Easter weekend.
Seed, who does not pay taxes, claims no benefits and rarely uses a bank account that was deprived of detention for three years before police raided Islington, north London on March 27 last year.
The electronics expert told a jury at Woolwich Crown Court that he was not the man the rest of the gang called "Basil."
However, on Friday he became the 10th person to be convicted in connection with the crime when he was convicted of the Hatton Garden Safe Deposit Company's conspiracy and the debt of the proceeds.
Seed was released during the bank holiday weekend in August 2010 with members of the same gang conspiring to disappear the Chatila jewelry store on Bond Street.
The prosecution had claimed that he had pretended to be a BT engineer before the intrusion of the security system and then used a 2G cell phone to block the alarm.
The thieves could not drill into a vault containing 40 million pounds of gems, but were sold out of display cases worth £ 1 million worth of jewelry.
The jury, consisting of six men and six women, consulted 35 hours and 35 minutes before resetting their verdicts on Friday.
Seed, who grew up in Cambridge, seemed momentarily blank after returning the sentences. The judge, Christopher Kinch, QC, said he would sentence him later on Friday.
Seed's two Hatton Garden ringleaders, Brian Reader, 80, John Kenny Collins 78, Daniel Jones 64, and Terry Perkins, who died in prison at the age of 69 last year, were all imprisoned in 2016.
Collins and Readers have been released, but they will have to go back to jail if they can not repay more than £ 6.5 million of the proceeds that the police believe could still be under their control.
Detectives believe that the gang had operated undetected for decades before they were caught but could not connect them with other crimes.
Seed traveled abroad three times after being photographed by a surveillance team for the first time in the weeks following the Hatton Garden collapse when he was unknown to the police.
Philip Evans, who was responsible for prosecution, suggested Seed, who studied electrical engineering and physics at Nottingham University. He may have brought stolen money to Portugal, where Perkins had an apartment in the Algarve.
Seed was identified by the Flying Squad in late November 2015. Additional surveillance footage showed that he walked through Canary Wharf in April 2016.
But by March last year, detectives were waiting to catch seeds with more than 1,000 items stolen from the Hatton Garden.
It was believed that he melted gold and broke jewelry on his bedroom bench when he was taken from a larger storage bin.
Dr. Gordon Burrow, a gait expert, compared covert shots of Seed with CCTV imagery of Basil, clad in a ginger wig, face mask and hat while carrying a black garbage bag to and from the scene to cover his face in front of the cameras.
He told the jury that the "unusual" Hinker supported the charge that Seed Basil was.
The prosecution reported that electronic devices in his home, including an alarm center and a mobile jammer, were being used for the training, and suggested that he might have worn a BT uniform to gain access to the buildings prior to the crime.
Evans said, "Especially for these two offenses, very special skills and knowledge were needed to circumvent the alarms and security measures in the premises.
"The prosecution suggests that Mr. Seed is one of those people and has the necessary skills and knowledge to support the successful conduct of these crimes."
Seed claimed he could have gone on a family vacation in Cornwall, or visited his elderly mother at Cambridge at the time of the Hatton Garden burglary, and told jurors that he had never been known as Basil.
"Everyone calls me Basil now," he said. "I'll be known as Basil for the rest of my life."