A housing benefit officer with the London Borough of Ealing reopened thirty-four dormant claims and paid £280,000 of taxpayers money into his own bank accounts.
Even after civil servant Mark Hypolite, 36, was caught and banned from his office he sneaked back in and logged-on to a council computer and continued the fraud.
Hypolite, of Phipps House, Shepherd's Bush was bailed to return to Isleworth Crown Court for sentencing on December 3 on condition he does not enter any London Borough of Ealing premises except on legitimate business.
Today the jury found proved nine sample counts of dishonestly making false representations between April 12, 2010 and November 16, 2011.
Hypolite changed his name by deed poll to open bank accounts under different identities and immediately withdrew the payments in cash.
The council have recovered £97,000, but do not know what has happened to the remainder or what Hypolite spent the money on.
The defendant was employed at Perceval House, Uxbridge Road from 2007 and was identified by colleagues who suspected suspicious activity, resulting in him becoming the target of an investigation by the audit department.
The thirty-four claims were reopened without the original claimants' knowledge and paid into three different bank accounts, one of which was in the name of Hypolite's mother's second husband.
Prosecutor Mr. Mark Tomassi told the jury: "He was employed by the council and was not entitled to the monies paid out. It was pure fraud from first to last.
"The frauds committed by Mr. Hypolite are complicated, sophisticated, persistent and consistent and a very large sum of money has been wrongly diverted.
"This all points to a sophisticated, calculated successful fraud.
"He was suspended and told not to enter the premises and knew he was not welcome within the council offices, but was seen there again a few days later."