He was a senior British civil servant who previously served as the director of the signals intelligence and cryptography agency the Government Communications Headquarters (GCHQ) and established the UK's National Cyber Security Centre.

[11] Hannigan appears regularly in other accounts, notably by Blair's Chief of Staff Jonathan Powell, attending private crisis meetings with Irish Republican leaders, including Gerry Adams and Martin McGuinness, at Stormont Castle and Clonard Monastery.

[30] On his first day in the role, Hannigan wrote an article in the Financial Times on the topic of Internet surveillance, stating that "however much [large US technology companies] may dislike it, they have become the command and control networks of choice for terrorists and criminals" and that GCHQ and its sister agencies "cannot tackle these challenges at scale without greater support from the private sector", arguing that most Internet users "would be comfortable with a better and more sustainable relationship between the [intelligence] agencies and the tech companies".

Since the 2013 surveillance disclosures, large US technology companies have improved security and become less co-operative with foreign intelligence agencies, including those of the UK, generally requiring a US court order before disclosing data.

Interviewed alongside his former counterpart Admiral Michael Rogers, Head of the NSA and US Cyber Command, at the 2017 Aspen Security Forum, Hannigan said that since 2014 the companies had accepted responsibility for the content they carried and were making progress on extremist material, pointing to Mark Zuckerberg's comments on the subject.

[43] In a speech welcoming the Queen and Prince Philip, Hannigan described the historical line between Bletchley Park and the NCSC and set out the challenge of cyber security at a national level.

In a speech in November 2015, he said that the usual market mechanisms were failing on cyber security: "The normal drivers of change, from regulation and incentivisation to insurance cover and legal liability, are still immature".

[53] In December 2017 he joined General Lord Houghton in drawing attention to Russian threats to undersea internet cables, endorsing a report by Rishi Sunak MP for the Policy Exchange thinktank.

"[29] In February 2017, Hannigan was appointed to the UK Government's new Defence Innovation Advisory Panel, along with McLaren Chairman Ron Dennis and astronaut Tim Peake.

Hannigan had in fact resigned because he had given a character reference some years earlier while working in the Foreign & Commonwealth Office using his FCO title, for Father Edmund Higgins, who had been found guilty of possessing 174 child pornography images, but the priest later reoffended.

He was also heavily criticised in the ISC report for later revealing operational information on a TV programme of how intelligence agencies had discovered the identity of Islamic State executioner Mohammed Emwazi, commonly known as Jihadi John.

The successor Director of GCHQ had written to Hannigan to remind him of his ongoing responsibility to safeguard sensitive information and to seek approval in advance of discussing such matters in the media, but without any substantive sanctions which the ISC viewed as giving the wrong message to other former intelligence staff.