Einar Wegener would kill himself in the spring. He had chosen a date – May 1, 1930 – after a year spent in torment. The cause of his suffering was quite simple: he was sure he was a woman, born into the wrong body. Or perhaps it was more complicated: sometimes Wegener, whose life is soon to be portrayed on film by the Oscar-winning British actor Eddie Redmayne in The Danish Girl, felt he was two people in the same body, each fighting for supremacy.

One was a Danish landscape painter, a steadfast man who, in his own words, “could withstand storms”. He was married to a woman whose strength and talent matched, or perhaps even surpassed, his own: Gerda Wegener, a successful Art Deco illustrator who produced portraits of fashionable women for magazines such as Vogue and La Vie Parisienne.

The other shared none of these qualities. Lili Elbe was, as she set down in letters and notes for an autobiography, a “thoughtless, flighty, very superficially-minded woman”, prone to fits of weeping and barely able to speak in front of powerful men. But despite her womanly defects, by February 1930 she was becoming too powerful for Wegener to resist. “I am finished,” he wrote at the time. “Lili has known this for a long time. That’s how matters stand. And consequently she rebels more vigorously every day.”