At first glance, it is difficult to conceive of Nos Invisibles (1907) as a controversial text. Its pages contain dreamy ruminations on the quest for spiritual serenity and “the mystery of eternal life”, interspersed with elegant illustrations by the Italian watercolourist Raffaele Mainella that conjure celestial bodies and the healing power of nature.

When I was a child, my dad used to tell a funny story about my brother falling out of a window. Louis was five at the time, and they were at my grandmother’s flat in the north of England. It was an ex-council housing complex, the ceilings were mean and low, but it was the second floor nonetheless…