The UBS accountant who last year scrutinised Kweku Adoboli’s trading activities – before revelations of an alleged $2.3bn unauthorised loss at the Swiss bank – questioned the existence of counterparties on transactions booked by the former trader, a jury heard today.

William Steward, an accountant in UBS's back office who had been trying to make sense of Adoboli's trading books last year, took the witness stand at Southwark Crown Court for a second day.