The designated location is Gustoso, a modest Italian restaurant in Pimlico, central London. The booking is under my name. Security: light to invisible. Sipping a Virgin Mary, I savour the moment ahead of the first on-the-record interview with the Chief of MI6, Britain’s Secret Intelligence Service (SIS).

Gustoso is suspiciously thin on customers and the cheesy Italian music is a distraction. Sir John Sawers slips almost undetected into a wooden chair to my right. Britain’s spymaster is tall and trim, a sporty 59-year-old blessed with a full head of black hair, a few grey flecks and Ealing studio looks. More flashy Pierce Brosnan than world-weary Alec Guinness. After a brief exchange about our summer holidays (his interrupted by the beheadings of two American hostages by Islamist jihadis), I ask the obvious question: why are you having lunch with me on the record? I thought SIS was supposed to be secret.

“It is secret,” replies Sir John. “But it is important that people understand a bit more about why intelligence is necessary?.?.?.?There always used to be a presumption that the intelligence services were on our side but things like Snowden [Edward Snowden, the renegade US national security agency contractor now in hiding in Russia] have led some people to question that. I still think there’s overwhelming support for us but there’s also a louder voice of criticism, a questioning, ‘Are we really necessary?’?”