“This is the kind of thing he sends me,” says Robert Harris, getting up towards the end of our interview in the Fitzwilliam Hotel, to show me a video clip mailed to him earlier by none other than legendary film director Roman Polanski.

It turns out to be some hilarious footage from the Iranian coverage of this summer’s Olympics, in which the skimpy outfits during the gymnastics are covered by black bars. After we’ve both finished laughing, Harris says with a glint in his eye, “Typical Roman!”

The association between Harris – who is in town to promote his excellent new Vatican thriller Conclave – and Polanski goes back to the author’s 1992 alternative history hit Fatherland, which the director wanted to film. Although he failed to realise that ambition, he remained a keen fan of Harris’ work and was particularly taken by his ancient Roman thriller Pompeii, influenced as it was by Polanski’s 1974 neo-noir masterpiece, Chinatown.