Back in 2017, we made Slow Horses by Mick Herron our Thriller of the Month in August and a whole host of readers found their new obsession. Now, 15 years on from its first publication, we sat down with the author of 9 novels and 5 novellas in the series to discover how it all began, what he thinks are the most important elements of his writing and where his cast of sidelined spooks find themselves in the new novel, Clown Town.