In his 15th work of fiction, Sweet Tooth, Ian McEwan revisits the all-encompassing "strife" of the early 1970s to present a threadbare and fractious Britain which its loudest voices believe to be falling into "decadence, decay, decline, dull inefficiency and apocalypse". If I had interviewed him even a couple of months ago, those "plus ca change" cliches might have sprung on to the keyboard almost unbidden. Yet, when we did meet, the sun was shining, hard and hot, over a festive London on one of the final golden days of the Olympics.
"This is the first time in the national narrative that I remember when people have actually said we are living through good times," McEwan says. He has recently "downsized" in the capital, keeping a flat in Bloomsbury while moving to the Cotswolds with his wife, journalist and novelist Annalena McAfee, and looks on the happy city with pleasurable amazement.
"I've never known London in such a good mood. I've never spoken to so many strangers. It might just be a weird delirium, like something out of A Midsummer Night's Dream. It is a curious moment."
A novel about espionage and fiction that traces the overt and covert connections between secrecy, deception and creativity, Sweet Tooth expertly navigates the gulf between perception and reality. Its feints and ruses prompt the thought that "all novels are spy novels". For all its critique of state-supported subterfuge, McEwan muses that, "The end of secrecy would be the end of the novel - especially the English novel. The English novel requires social secrecy, personal secrecy."
An MI5 colleague of its secret-agent heroine re-defines the "line" between "what people imagine and what's actually the case" as "a big, grey space, big enough to get lost in". Into that collective space have tumbled fears and fantasies about the end of the world and the demise of a nation alike. McEwan has returned time and again to the end-time mindset, in stories shadowed by images of breakdown, catastrophe and entropy in family, society and eco-systems - from First Love, Last Rites in 1975 to Solar in 2010. Yet he harbours doubts of our beloved tales of descent.
"I'm not sure I believe in cultural decline," he argues. "Martin" - his old friend Martin Amis - "takes his father's view that we're all going to hell - I always disagree with him on that. I just think there's general cultural amnesia about how it was for most people in the 50s. But what's not at issue is the endless discussion of economic and political decline which dominated the 70s."
McEwan enjoyed the time-slip return to the politics and culture of his youth. Sweet Tooth recaptures an awkward age with a veteran's inwardness and a sleuth's tenacity rather than a glib pop-historian's hindsight. "It was a chance to re-examine a lot of things. I was 22 in 1970. I was very politically aware and read lots of newspapers - aware of all the things that were happening: the states of emergency, the strikes, the general sense of doom and decline. But I didn't really care. I felt that I had no stake in it. I had two pairs of jeans and five T-shirts and my flat cost £3 a month."
Born in Aldershot, south-west of London, in 1948, McEwan is the son of an army officer who had fought at Dunkirk in 1940 (and whose ordeal during the retreat found its way into Atonement). He moved from the peripatetic childhood of an army family to a state boarding grammar school in Suffolk, then to Sussex University. After graduation came his stint as Malcolm Bradbury's first-ever creative-writing student at the University of East Anglia, in Norwich.
That proved the seedbed for the neo-gothic virtuosity of his early stories - which the new novel teasingly passes through another lens. Its author-figure, Tom Haley, pens eerie and morbid tales that recall McEwan's own first efforts in mood but not in style. Tom even publishes an apocalyptic novella about a ruined Britain that sounds much like Cormac McCarthy's The Road but in fact derives from a dystopian fiction McEwan wrote but abandoned around this time. For the evidence, see "Two Fragments: 199-" in his 1978 collection In Between The Sheets.
Sweet Tooth also takes us to the Sussex campus. Our narrator is brisk, bright but vulnerable Serena Frome: a bishop's daughter and a Cambridge mathematics graduate with a greedy but untrained taste in fiction. "I thought I'd play to a kind of sexism in the reader by giving her a kind of muscular intelligence," says McEwan.
Drawn into the security service after an affair with a dashing, enigmatic historian at Cambridge, Serena travels to Brighton to recruit Tom for an MI5-driven stunt without blowing her cover as the representative of a philanthropic foundation. Her bosses plan to fund, through a covert channel, a group of liberal intellectuals with proven doubts about the Soviet system, and so enlist them as unwitting Cold Warriors.
Many literary histories tend to depict Britain in the early 1970s as a moribund landscape peopled by dull realists, waiting for the magic wand of Amis, McEwan and Co to awaken it. Sweet Tooth, and its author, challenges this myth. McEwan notes the prestige of heavyweight innovators such as publisher John Calder and novelist Anthony Burgess. In Sweet Tooth, Serena - a devotee of realism who believes author and reader share "a contract founded on mutual trust" - tussles with the modernist aesthetics of her protege, Tom. For him, "it wasn't possible to recreate life on the page without tricks". To which camp does Sweet Tooth belong? Suffice to say that, with all his cunning and dexterity, McEwan always knows how to add "one extra fold to the fabric of deception".
For Serena's clandestine employers, this fancy culture is a sideshow - albeit an exploitable one. So have I missed some crucial hidden history about MI5 and the literary scene? Apparently not. "I don't think MI5 ever backed 10 writers and academics - I just hope the sleight-of-hand works." For the shabby-sinister and sexist atmosphere of the security-service HQ, staffed by cynical and crabby shadow-warriors and keen, clever young women stuck in menial jobs, McEwan did consult a certain David Cornwell - better known as John le Carre. The novelist and ex-spook proved "very generous" with his reminiscences, and helped McEwan to bottle the smoke-and-mirrors aura of secret bureaucracy.
"Because you didn't know what other people around you were doing, you couldn't tell whether they were complete idiots or unbelievable geniuses. You never knew."
Sweet Tooth (Jonathan Cape $37.99) is out now.