Few figures in literature have been as passive and undemonstrative as George Smiley. And yet, right there in the second chapter of Tinker Tailor Soldier Spy, the spirit of le Carré’s intelligence agent was uncharacteristically lifted by a humble bookshop. Smiley, we’re told, “approached Heywood Hill with a merry heart.”

Which isn’t to say that Heywood Hill is any old bookshop. It’s been a stalwart of Mayfair’s Curzon Street since it first opened, in 1936, and the frontage includes two significant fixtures: a Royal Warrant (Heywood Hill was, it is said, Queen Elizabeth II’s favorite bookshop) and a blue plaque, reminding visitors that Nancy Mitford had worked there for three years during the Second World War. During that period of time, Evelyn Waugh described Heywood Hill as “a centre for all that was left of fashionable and intellectual London.

A stalwart of Curzon Street since its opening, in 1936. The blue plaque reminds us that Nancy Mitford worked there for three years during the Second World War.

Now run by Nicky Dunne—son-in-law of the shop’s owner, the 12th Duke of Devonshire—Heywood Hill has seen few changes since those days. Stepping inside the chandelier-lit town house still offers the same sensation of hushed calm that good bookshops always have. But under Dunne, Heywood Hill has become less about what it can offer customers who walk through the door and more about what it can send across the world to them.

A decade ago, Heywood Hill launched its A Year in Books subscription service, posting a steady stream of titles to its base of international, interested readers. Most popular is its Tailored service, which is so popular that the shop has been forced to limit it to 1,000 customers a year. After an initial consultation, the Heywood Hill booksellers scour the British publishing landscape to find the 12 books that most closely align with the reader’s interests. Dunne calls it “the world’s most personalised book subscription.”

Dunne calls it “the world’s most personalised book subscription.”

Which brings us to Tradecraft, the shop’s newest subscription service. Although not personalized, it has a laser focus on the spy genre. And this is for good reason, since Heywood Hill is arguably the most spy-centric bookshop on the face of the earth.

Its Tinker Tailor Soldier Spy name-drop came about because le Carré was a regular customer, for the shop is located a stone’s throw from the old M.I.5 headquarters in Leconfield House. The British outpost of the C.I.A. was just around the corner. As such, spies made for some of the shop’s most loyal customers. Indeed, pressed on Heywood Hill’s link to international diplomacy, Dunne admits that “a meeting once took place in the basement here between a British prime minister and a foreign minister.” When? A pause. “At some point this century.” Another pause. “But I don’t want to overemphasize that.”

The books offered in the Tradecraft service are all taken from Dunne’s list of the 50 greatest spy novels published since 1900. It’s an impressive collection, starting with Rudyard Kipling’s Kim, from 1901, and ending with Rachel Kushner’s Creation Lake, from earlier this year. Between them are wall-to-wall classics. The Scarlet Pimpernel is there, as is Live and Let Die. There’s Conrad, there’s Priestly, there’s Christie and Greene and Forsyth and Herron.

Heywood Hill’s rare-books department.

More than anything, the list is proof of just how absurdly enduring espionage books can be. Key to this longevity, Dunne says, is the fact that “the geopolitical background might always be shifting, but very little changes in terms of human motivation. Whether it’s human or organizational machinations, those motivations tend to be familiar.”

Plus, don’t forget that they’re actively useful to the trade. One of Dunne’s customers is a retired C.I.A. operative, whose chief mandated that all his staff submit book reports of all the latest spy novels, in case one of the authors had come up with some ingenious new technique that hadn’t been covered during formal training. “They needed to know if anyone had thought of something they hadn’t,” says Dunne. “Reading novels was a practical exercise for them.”

Stuart Heritage is a Writer at Large at AIR MAIL. He is the author of Bald: How I Slowly Learned to Not Hate Having No Hair (And You Can Too)