"Are you interested in food?" John Lanchester asks.
We are at a table at the Dairy, a highly regarded restaurant in Clapham, south London, which is decorated in bucolic style to match its natural ingredients including vegetables grown on its rooftop.
It is a deceptively simple query, like others he later lobs at me during our meal. Lanchester's most recent books – his 2012 state-of-London novel Capital, his 2010 account of the financial crisis, Whoops! and his new book, a tongue-in-cheek lexicon called How to Speak Money – relate to finance and the societal distortions it has created. But his first novel, The Debt to Pleasure (1996) was a Nabokovian mystery written in the form of a cookbook by Tarquin Winot, a prickly intellectual snob.
In other words, Lanchester, 52, is a man of playful humour and wide-ranging erudition. Born in Hamburg and brought up in Hong Kong, where his novel Fragrant Harbour (2002) is set, he attended a boarding school in Norfolk and then the University of Oxford, where he tried postgraduate research. Bored with that, he turned to literary journalism, working at the London Review of Books as an editor before switching to full-time writing.
In a mauve shirt and a black jacket, he looks like an off-duty bank manager of the old-fashioned kind, who would decide on your creditworthiness by looking you firmly in the eye and asking some astute questions rather than with a computer. His father, who died when Lanchester was 21, was a banker at HSBC in its colonial days, when its expatriate recruits lived in a facility called the Mess, midway up the Peak in Hong Kong.
By "interested in food", Lanchester turns out not to be asking whether I'm hungry, but if I'm familiar with Europe's finest eating places. He recalls a visit to Mugaritz, a two-Michelin-star restaurant near San Sebastián in Spain.
I'm open to it, I respond guardedly.
How, I ask, are they killed?
No, I say, straight question. How are they killed?
Like a peer-to-peer network? I suggest.
"This is your sourdough bread and a smoked bone-marrow butter," the waitress says, placing them on the table. The fresh-baked bread is warm and wrapped in a linen bag. The butter is a pat smeared to the side of what looks like a baked potato. I tap it cautiously and discover that, in a reversal of the Mugaritz trick, it is actually a chilled stone.
"I wouldn't go for it, although you probably have very good dental insurance at the FT," Lanchester says.
In How To Speak Money, Lanchester writes about what he calls the "reversification" of banking, in which the true nature of financial instruments is hidden by describing them as something that sounds better, such as debt being called "credit". I compare this with the modern trend in cuisine, with professionals thronging to artisan restaurants. We all go to places where they've churned the butter, I say mockingly.
"Though try the buttered bread before you diss it too robustly," he interjects. It is delicious, and I am munching it when the waitress returns, bearing a wicker basket. "Home-made curd with mushrooms, and honey from our rooftop bees," she says, spooning out an amuse-bouche.
Mention of his mother prompts me to say how touching I found his memoir Family Romance (2007), A big lie forms the heart of it. His mother, who was nearly 40 when she met his father, hid her age by using her younger sister's passport, then cut herself off from her family to avoid detection. Lanchester was an only child, and she suffered four miscarriages as she tried to bear more.
"I think she saw it as a single decisive act, but a lie like that is like having a blackmailer. You're blackmailing yourself," he says.
In the book, Lanchester relates the hidden tension in his parents' relationship to his own sense of anxiety, which spiralled in adulthood into agoraphobia, to the point where he could not cross open spaces.
Does he still think of himself as very anxious?
Could he walk across Clapham Common? I say, pointing out of the window of the Dairy.
"Oh, yes. Absolutely," he says confidently.
When was the last time he wouldn't have been able to?
That was not long ago, and I remark that Capital, his novel about the struggles and tensions in a typical Clapham street in the bonus-obsessed age, made me feel anxious, so well does he capture the struggles of Londoners to keep up appearances in a world of escalating house prices.
I say that's what I like about it. I grew up in London and this incarnation is far preferable, despite the strains it creates. People may look back in 20 years and remember this as a golden age.
After finishing our first courses – truffle Brie with walnut bread, and chicken liver mousse with rhubarb and apple – we have eaten two vegetable dishes. The food is delicious, and when the waitress arrives with more dishes I realise that I have out-consumed Lanchester, who has paced himself better.
"This is the famous intelligent octopus," he says.
It doesn't look very intelligent, I say.
The fish is as good as Lanchester promised, full of sharp flavours that meld in unusual ways. I ask why he delved into financial non-fiction in both Whoops! and How to Speak Money. Along with Michael Lewis, he has become one of the world's most popular and accessible writers on finance.
I tell him I found the book entertaining and lucid – its brief explanation of the bond repo market is the only intelligible account I have read. Ultimately, however, I felt I learnt some useful things while enjoying myself, rather than being thoroughly educated about the world's financial system.
How many people without a professional interest can truly understand money? I ask. After all, a lot of modern finance has been made obscure by bankers to stop outsiders from competing with them, or customers being able to demand better terms.
What worries him most about British society?
The final courses come, although we are both full: rump of lamb with broccoli, anchovy and capers; and chicken oysters with wild mushrooms and asparagus. The chicken's skin lies in crisp, folded layers and we examine it carefully to work out how the chef achieves the effect. "It must be dehydrated. They have a machine," he concludes.
We eat all we can and order two espressos, unable to fit in dessert. I ask how Lanchester decides what to do next, given his eclecticism. Does he feel impelled to write a book quickly because he needs the money?
So what is he working on now?