The pensioner's accounts were completely emptied
Mortgage broker Neil Williams, 31, from Caerphilly, stole more than £70,000 to finance a lifestyle he could not afford, completely emptying his 80-year-old grandmother Rachel Williams' bank accounts.
Cardiff Crown Court heard Williams, a married father-of-four, then tricked the pensioner into mortgaging the house she had lived in for half a century and owned outright - even earning himself commission on the deal.
She is now taking civil legal action against her grandson because her semi-detached home in one of Cardiff's affluent suburbs is still at risk because of the outstanding mortgage.
Prosecutor Elizabeth Pearson told the court how widowed Mrs Williams became a "victim of her grandson's duplicity".
Williams admitted 11 counts of theft and two of deception.
Jailing him for 18 months Judge Eleri Rees said: "It is difficult to think of a greater breach of trust both on a family and on a professional level."
Miss Pearson said Williams obtained his grandmother's savings account and over two years removed £19,000.
"Neil Williams worked as a mortgage broker and a financial consultant," she told the court.
"He made an application for a mortgage on his grandmother's home and submitted a forged signature.
"He then persuaded her to sign the deeds for the £51,900 lump sum mortgage.
"He even earned himself £520 commission as the broker."
Mrs Williams, from Llanishen in Cardiff, only became aware of the crime six months later when she began to get letters from the mortgage firm.
She checked her bank account and the found her life savings had disappeared.
Defending Williams Jim Conod said he had acted "out of desperation".
"Williams had got himself in a position where he was living a lifestyle he couldn't afford.
"He was in way over his head. He said he felt like a cornered animal," Mr Conod said.
"But he has learned a lesson to be open and honest with yourself in business."
Williams, a partner in a south Wales mortgage brokers, was ordered to pay back £19,000 to his grandmother.