A fraudster who stole more than £120,000 from his in-laws has been imprisoned for five years after leaving his family "decimated," a judge said.

Dan Jacobs, 39, a former member of Borehamwood and Elstree Synagogue in Hertfordshire, had admitted on Monday to five counts of fraud committed over nearly five years.

He took a total of £120,573 from his wife's parents and elderly grandmother, who lives in a care home, through what both the prosecution and the defence referred to as an elaborate "web of deceit".

Passing sentence, Judge Ian Stern told Harrow Crown Court on Friday that Jacobs had subjected his family to a "frankly unbelievable" level of deceit.

"You completely controlled your father-in-law and mother-in-law and the grandmother," he added.

Mr Dominic Bush, prosecuting, said that the fraud had left his family "living a hand-to-mouth existence.

"His wife would suck on ice cubes to keep the hunger pangs at bay while he was spending all the family's money. [His father-in-law] wasn't able to go to the dentist, and so went three years with an untreated dental condition."

Between 2010 and 2015, Jacobs deceived and scared his family into handing him full control of their finances to fund his gambling addiction, which saw the former Borehamwood eruv committee member visit a casino 2,000 times in the space of eight years.

Jeffrey Israel, defending, said Jacobs's addiction began after his son was born in 2006 and immediately diagnosed with serious heart conditions, requiring open-heart surgery when he was a week old.

Mr Israel said the son was at Great Ormond's Street Hospital, which is "round the corner from a casino were most of his gambling acts took place. When he left the hospital one evening he met another father who convinced him to go to the casino, and he spent the rest of his time not taking care of his family, but at the casino, gambling."

After another operation on the son in 2008, in which the boy's heart was restarted, Mr Israel said that "the casino visits became more frequent, the bills went unpaid, he moved into a bigger house with a bigger mortgage while living the lie, making his financial position more difficult."

Addressing the issue of Jacobs' son in his sentencing, the judge said: "The fact that you had an ill son and over that time you deprived him of money because you needed to spend it on your gambling addiction frankly defies belief."

Jacobs was fired from an accountancy firm in 2010 after using a company credit card to pay himself approximately £200, an offence which he was cautioned for at the time.

Mr Israel said that without the ability to gain further employment in his field after his caution, Jacobs fell into full-time gambling, "dragged into the abyss, into casinos, as it was an escape from his home life.

"He lied and lied to the extent that when his son had to leave the state school he was in because he was being bullied for being Orthodox and was sent to a private Jewish school in Bushey, he couldn't pay for that after six months. So his son, at age 12, lost a full year of schooling."

The Dutch-born father of four moved his wife and children to live with the in-laws after his own home was repossessed in 2011, though he did not admit this to his relatives, instead telling them a tale involving the secret service.

Mr Bush said: "We know [the repossession] was very likely to do with the gambling and the finance difficulties he had, but at the time he said this was the result of some fraud that had been perpetrated against him.

"And he spun a very elaborate lie, saying that the secret services, MI6, were investigating, and as a result the family weren't to touch their bank accounts at all, and they weren't to open any mail addressed to them."

Mr Bush then proceeded to tell the court how Jacobs had "invented a person called Jake, who was supped to be their buddy from MI6, and his own wife and other family members were in contact with Jake, who was obviously the defendant.

"He controlled every aspect of their lives; they were in total and utter thrall to him."

Jacobs, a former yeshiva student, continued to defraud his in-laws for nearly four years while living under their roof, using cash machines to withdraw money from five bank accounts belonging to the family.

Mr Bush explained that he achieved this through intimidation, saying: "The family were living in constant fear that if they disobeyed the orders the defendant was giving them two things would happen: they would lose their house in the same way his went, and his wife was terrified she would lose their children.

"It was made clear to her that if [his] orders weren't followed, the house would go and the children would go."

He stole most heavily from his wife's grandmother, transferring a total of £57,953 from her saving accounts to her current accounts before withdrawing all of it in cash between February 2012 and August 2013.

He also took more than £52,768 from two accounts belonging to his father-in-law, a retail executive.

Jacobs raided his first account between August 2010 and September 2011 and the second between August 2012 and May 2015.

Jacobs, who founded consultancy firm Develop Your Business in 2010, also stole £9,850 from his mother-in-law's account between September 2010 and April 2012.

Jacobs, of Red Road, Borehamwood, was on the committee that campaigned to establish an eruv in the town. He left the team once plans were set in place but before the eruv became functional in 2010.

Two years before Jacobs started defrauding his in-laws, his wife took part in a 5km charity run to raise funds for a hospital whose doctors and nurses helped to save his son, who required open-heart surgery three times before his third birthday.

A senior figure in the Borehamwood community said Jacobs gave up his synagogue membership some time ago, adding: "The whole thing is a shame."

Jacobs attended the Maimonides school in the Netherlands before meeting his wife and emigrating to Britain in 1997, where he worked for accountancy firms KPMG and Arram Berlyn Gardner.