Mohammed Ahmed was unhappy with what he called a ‘toxic’ work environment so he decided to use his trusted position at Barclays bank to transfer all but £80,000 from 75-year-old Brian Mahoney’s retirement fund.

Not content with his first fraud, the next month he set up five fake bank accounts each with £5,000 overdrafts, swindling another £25,000.

Jailing Mohammed Ahmed for three years the judge, Roger Chapple, said: “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,” the Islington Gazette reports.

Ahmed had obtained Brian Mahoney’s details when he was given them, before ringing up the pensioner to offer him a new account.

Brian Mahoney described in court the shock and worry he felt when he rang up two months later to check interest rates and then discovered all of his life savings had disappeared.

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

He pleaded guilty to two counts of fraud but denied two further counts where he was accused and later found guilty of adding an extra signatory to Mr Mahoney’s account and transferring £826,710 out.

Judge Roger Chapple did accept he had been working in a ‘toxic’ environment where staff were put under a lot of pressure to reach unrealistic targets.

He also added that Brian Mahoney had suffered “very substantial stress and anxiety” after learning of the theft.