Management consultant Brian Chapman, 55, Binniehill Road, Cumbernauld, was struggling to maintain payments towards his mortgage and 12 credit cards at the time of the alleged con, the Old Bailey has heard.
Chapman, who worked at KPMG's Canary Wharf office and would regularly stay overnight at the Hilton hotel, said his main client at the time was High Street bank HSBC.
"My client was HSBC which was bringing separate smaller businesses together into a global model," he explained. He was earning a gross annual salary of more than £100,000 but was £90,000 in debt and lost an average of £330 a week gambling, the court heard.
Chapman allegedly double or even triple-claimed the same expenses, including flights, hotels and mobile phone bills.
Giving evidence he denied making any false claims and insisted his finances were "manageable".
"It was manageable, it was survivable, it was not ideal but with a long-term strategy it was under control," he said. "Ideally I expected to retire at the age of 65 and did not expect to retire in debt."
Chapman denies a single count of fraud.
The trial continues.