Dhaka, July 12 -- In September 2015, at a discreet meeting in London, senior executives from the French technology firm Oberthur were introduced to a man known simply as "Mr. G." To them, he was a powerful insider - someone close to Bangladesh's prime minister, with the influence to open doors, steer policy, and secure contracts.

To the World Bank, which had already begun investigating the deal, he was the keystone of a multi-million-euro bribery scheme.

For nearly a decade, this man's identity remained concealed in court filings and confidential memos. He was referred to as "G" by World Bank investigators and as "the General" in internal company emails.

Only through persistent reporting, stretching from Dhaka to Washington and Paris, ...