Reading these two books, which are very different, though they cover the same territory, I was reminded of the day Alan Rusbridger, then editor of The Guardian, beckoned me into his office. When I confirmed that I had my mobile phone with me, he immediately told me to leave it in another room. He had learned, from a source he was about to reveal, that intelligence agencies can use mobile phones to track people’s movements and bug conversations, even when they are switched off.

It was an agonising time. Rusbridger faced a difficult decision, perhaps the most difficult of his long career as an editor: whether to publish a huge cache of secret documents that would reveal how the US National Security Agency (NSA) and Britain’s GCHQ were routinely intercepting the communications of millions of innocent individuals, sometimes in cahoots with massive internet companies. If Rusbridger went ahead, he risked prosecution under the Official Secrets Act. A guilty sentence might mean a hefty fine, which The Guardian could ill afford, or even jail.

As these books show, The Guardian was not the first media organisation approached by Edward Snowden, the now well-known NSA contractor turned whistleblower (or traitor, as some in the US and UK security and intelligence hierarchies insist). At the centre of his attempts to release the files he had downloaded,