According to a website Nick Harkaway recently checked, the median age for a Hampstead resident like himself is 38. While he guardedly admits to being a little older, it is nonetheless a stage in life at which fatherhood – a recurring theme in his latest novel, Tigerman – becomes a common issue.

In many ways, it is a subject the author will never be able to avoid; as well as having a three-year-old daughter and one-year-old son, his own father is no less than John Le Carre, the legendary writer behind stories such as The Spy Who Came In From The Cold and Tinker Tailor Soldier Spy.

When Harkaway eventually published his own debut novel, The Gone-Away World, in 2008, he found his writing often reflected whatever he was living through at the time. Where before that might have encompassed “ubiquitous self doubt” or the “inability to put oneself forward’, with Tigerman it was male identity.

“I think a lot of people feel… not exactly an uncertainty about what it means to be a bloke getting older and trying to find an appropriate pattern of behaviour,” he explains, “but it’s just that things in our father’s generation – the obvious certainties of what you should do, what was appropriate – were quite clear cut and those are definitely not the same now.

“When I was becoming a dad, my immediate instinct was to go to the bookshop and try to find a book about being a dad. I couldn’t find one that wasn’t effectively about how to remain a beer-swilling party animal while your wife’s having a baby. All I could see were these shelves upon shelves of recipes for divorce and I was quite surprised by that.”

Tigerman is the story of burnt out army officer Lester Ferris who, devoid of any family, is sent to wind down his career on the liminal island of Mancreau. A former British colony about to be destroyed because of its dangerous pollution levels, the island is a perfect breeding ground for every shady crime under the sun, from money laundering and drug factories to deniable torture centres.

Nearly 40 and nearly retired, Ferris initially obliges with his instructions to turn a blind eye to such business, but the unlikely emergence of a paternal friendship between himself and a sharp minded street kid sees him turn into self-styled superhero ‘Tigerman’ to protect his pseudo-son.

Even while writing about crimes with international repercussions, Harkaway says there’s nothing more serious than the relationship between his two protagonists.

“With all those other grand issues, what they come down to is how you try to create a space in which to have the relationships that matter. When people talk about national security, what they really mean is, ‘How do I create a space in which I don’t have to be worried about my children walking to school? How do I create a space in which I don’t have to worry about my wife or husband travelling back from work on the tube?’

“My educational background is on the history and practice of revolution and when you see what happens to start a revolution, it’s always very simple: it’s people feeling that their lives can’t be lived in the way that they believe they should be able to live them.”

Harkway’s own relationship with his father is healthy. While both writers have professionally shunned their original surname, Cornwell – for the younger, it was to stop his stories getting lost between Bernard and Patricia Cornwell on bookshelves – Harkaway appreciates Le Carre encouraging him to use his imagination from an early age.

“Ken Robinson, the educationalist, talks very compellingly about how we take fantasy out of kids as part of the schooling process. We basically say to them, ‘The various creative possibilities you’re coming up with aren’t appropriate for conversation. You shouldn’t be saying there’s a purple octopus under the lampshade because that’s absurd, you should be saying it’s got purple tassels.’

“My experience with writing is that it’s a thing that comes with taking the brakes off. I do look at my lampshade and think, ‘Gosh, I wonder if there’s a purple octopus under there.’

“I know full well there isn’t, just as children do, but it doesn’t mean that I can’t explore the possibility and go and lift up the lampshade.”

Nick Harkaway appears at the literary festival on Sunday 14 at 2pm. Tickets are £8.