Edward Snowden admits to John Oliver: I didn't read all of leaked NSA material

Oliver had gone to Moscow to meet the whistleblower and in his interview, despite the jokes, Oliver pushed him on whether he had read the documents he released in May 2013.

In the interview, the British comedian asked Snowden: "How many of those documents have you actually read?”

Snowden replied: "I’ve evaluated all the documents that are in the archive.”

Oliver then pressed the whistleblower further, arguing that to "evaluate" did not mean that he had read them all.

The former NSA contractor handed over a series of top-secret documents to reporters, which detailed the agency's mass surveillance techniques.

Oliver questioned Snowden about the damage his leaks may have caused, citing the example of a document published by the New York Times without a proper redaction. Oliver claimed it exposed intelligence work on al-Qaeda in Mosul.

Snowden admitted that was a "problem" but Oliver went further and said: "Well, that's a f***-up," which the whistleblower accepted.

Later in the interview, as Snowden explains the rewards were worth it, despite his fears it would go un-noticed and be a "three-day story".