[4] With his colleague Rob Evans, Leigh published a series of corruption exposures in The Guardian about international arms giant BAE Systems.
After a criminal inquiry by the US Department of Justice and other international prosecutors, the company was eventually required to pay penalties totalling $529 million.
[8] In 2010 Leigh was a member of the team which handled the release of United States diplomatic and military documents which had been passed to WikiLeaks, and which worked closely with Julian Assange.
"[9] In 2011, Leigh co-wrote a book with Luke Harding called WikiLeaks: Inside Julian Assange's War on Secrecy, which was published by the Guardian.
"[15] In a further spat in 2012, Assange referred in a press release to: "an information mule in the Israeli newspaper Haaretz, Yossi Melman, who conspired with Guardian journalist David Leigh to secretly, and in violation of WikiLeaks' contract with the Guardian, move WikiLeaks' U.S. diplomatic cables to Israel.
In 1985, he won Investigative Reporter of the Year in the Granada TV What the Papers Say awards, for exposing MI5 vetting of BBC staff.
Leigh and Evans were also presented with the Granada TV What the Papers Say Judges' Award for "an outstanding piece of investigative journalism that uncovered a story of great significance".
[19] In 2015, he and a Guardian team he led won Investigation of the Year at the British Journalism Awards for their exposure of tax-dodging at HSBC's Swiss bank.