On a blustery, bright spring day by the Thames, David Simon strolls into the River Café with an easy, unassuming stride, turning not a single head as he makes his way to our table. Only a mid-grey bomber jacket, emblazoned with the logo of the television series Homicide: Life on the Street gives any clue as to his identity.

Neither the name, nor the face, of Simon mean very much in this quietly chic corner of west London. We sit down and order the house prosecco, mixed with campari and blood orange. It’s an auspicious start. Simon is not known for the levity of his banter or for small talk, but he seems relaxed and in good humour.