A former News of the World investigative journalist has told an inquiry into press standards that his work had led to more than 260 "successful criminal prosecutions".
Mazher Mahmood, who was the defunct newspaper's investigations editor, told the Leveson Inquiry that his most high-profile probe had been into Pakistani cricketers who were subsequently convicted of match-fixing.
Mr Mahmood, who became known for disguising himself as a "fake sheikh" in order to carry out undercover reporting, said he had exposed "criminal and moral wrongdoing" during a 20-year career at the News of the World. He gave evidence in a room occupied only by lawyers to protect his identity. His words were broadcast to an annex where journalists and members of the public could listen.
Inquiry chairman Lord Justice Leveson, who is sitting at the Royal Court of Justice in London, said he had made an order allowing Mr Mahmood, who now works for The Sunday Times, to give evidence away from the public gaze for "good reason".
Mr Mahmood was asked to describe how the checks on his stories at The Sunday Times, where he now works, compare to those at the News of the World.
He said: "It was a lot more informal at the News of the World newspaper but in essence we still had to satisfy the same criteria. But it was a lot less formal - chats with the news desk - there were no meetings."
He added that the process at The Sunday Times is "a lot more stringent", but said that at the News of the World he was in "constant touch" with lawyers.
"Everything was discussed with the legal team," he said. "I couldn't go off-piste and do what I wanted. I had to take legal advice and throughout the investigation I remained in constant touch with our lawyers."
Mr Mahmood said that the two main questions to be answered when deciding if a story about a person should be investigated was: "Are they involved in criminality? Are they involved in moral wrongdoing?"
When Lord Leveson asked Mr Mahmood if he believed that if there was a conflict between what he perceived as a famous person's public persona and the story, then it was worth investigating. He replied: "If it's hypocrisy then very much. If they present themselves as wholesome characters and trade on that status then I think it's totally justified."