You have written a wide variety of books. Which was the most popular?
The Feckin' Book of Irish Slang was number one in the hardback non-fiction bestseller chart for six months, and it sold 80,000 copies. It was illustrated by Donal O'Dea and there was a series of Feckin' books.
That's feckin' great, but aren't you also a novelist of some renown?
I have also written historical novels. In 2013, I wrote Boycott, a story set in the Land Wars involving Charles Boycott, the land agent in Mayo. It was well reviewed and it sold reasonably well.
And tell us about your latest book, Fierce History?
It is really a book of anecdotes from history. They are the equivalent to the small stories from the newspapers that you come across by accident, as opposed to the big stuff. I like the story of Draco, the ancient Greek lawmaker who gave us the word draconian. He gave a speech and people started cheering and throwing their hats in the air. The story goes that he was killed by a bombardment of hats.
And you mention Dr Guillotin, who gave his name to the device used for French executions. Was the poor chap really against capital punishment?
He was opposed to executions, but believed that if they had to happen, there should be a device that chopped the head off quickly. He didn't actually invent the guillotine, but was saddled with the name.
On a happier note, which books would you take to a desert island?
I grew up loving classics like Silas Marner by George Eliot. Recently, I loved Little Fires Everywhere by Celeste Ng and Ancient Light by John Banville.
If you weren't a writer, what would you be?
I used to be a creative director and copywriter in an advertising agency. My main diversion when I am not writing is hillwalking. I have climbed every mountain in Ireland.