Each of Dan Brown's Robert Langdon books has involved lengthy research. Photo / Supplied
Each of Dan Brown's Robert Langdon books has involved lengthy research. 

The last time Dan Brown visited the Freemasons' Hall in Central London, he was discreetly researching his 2003 bestselling novel, The Da Vinci Code. A decade later, the New Hampshire-based author is launching his latest blockbuster, Inferno (Random House), in the ornate surrounds of the United Grand Lodge Of England's main headquarters.
"The Da Vinci Code was a double-edged sword when it comes to research," Brown admits. "On the positive side, I now have access to specialist curators and secret locations that realistically I never would have without it.
"But, simultaneously, I'm always trying to keep my topic secret - but whenever I show up at any of these places, the next thing you know there's a blog saying, 'Dan Brown was just at the Freemasons' Hall and he was looking at this particular medallion or floor tile. I wonder what he's up to?'."
Brown is forced to play a game of subterfuge with his over-eager fans, drawing attention to unrelated aspects before quietly concentrating on his real quarry.
"It's like leaving breadcrumbs in a different direction, which seems to have worked so far," he laughs.
Inferno sold more than 225,000 hardbacks in the UK alone during its first week of release, so there's little prospect of the otherwise unassuming 48-year-old going unrecognised. Even if, as tonight, he's dressed in a smart black suit and not the trademark tweed jacket his main protagonist, Harvard symbology professor Robert Langdon, famously also favours.
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