A banker who helped fraudsters steal �820,000 from a pensioner’s life savings was punishing his employers for forcing him to work in a “toxic” environment, a court heard.

Mohammed Ahmed, 26, of Durnsford Road, Bounds Green, used his trusted position at the Holloway branch of Barclays Bank to transfer all but �80,000 from a retirement fund belonging to 75-year-old Brian Mahoney.

The following month, he swindled another �25,000 from the bank after setting up five fake bank accounts, each with �5,000 overdrafts, Inner London Crown Court heard.

Mr Mahoney had told jurors of his shock and worry after realising almost all of his life savings were gone when he phoned to check the interest rate two months later.

Judge Roger Chapple accepted that Ahmed had been working in a “toxic” environment at the bank, with staff put under pressure to reach unrealistic targets.

But jailing him for three years on Thursday the judge added: “It was because you were prepared to use your inside knowledge of the banking procedures and the weaknesses you knew were in this system that this fraud succeeded.”

Ahmed was asked to contact Mr Mahoney, of Cuffley, Hertfordshire, to offer him a new account, for which he was given the details of the pensioner’s account.

He resigned from the bank on April 22, 2009, and was arrested on July 1.

Ahmed pleaded guilty to two counts of fraud. He denied two further counts relating to adding an extra signatory to Mr Mahoney’s account and transferring �826,710 out, but was found guilty after a trial.

Tim Forte, defending, said Ahmed had been under pressure in a “toxic” work culture and and “succumbed to weakness”.

Judge Chapple said Mr Mahoney had suffered “very substantial stress and anxiety” after learning of the theft.