UBS trader Kweku Adoboli charged with fraud
Mr Adoboli appeared before magistrates on Friday
Kweku Adoboli, the UBS trader alleged to have lost UBS $2bn (£1.3bn) in unauthorised trading, has been charged with fraud.
He has been remanded in custody until a committal hearing on 22 September.
The BBC has learned that UBS believes that the losses were accumulated in a large number of small trades over many months, not in one big deal.
UBS will give more details of his trading after the markets close on Friday afternoon.
Also, it turns out that he worked in the back office before becoming a trader, which may explain how he managed to keep his trading secret.
"This revelation, that it may have been almost impossible for UBS to spot Mr Adoboli's unauthorised dealings at an early stage, is expected to reinforce political pressure in Switzerland for UBS to hive off its investment bank," BBC business editor Robert Peston said.
Mr Adoboli, 31, is accused of carrying out unauthorised deals while working for UBS.
The Financial Services Authority (FSA), the City regulator, is investigating why the Swiss bank did not identify the trades