Lovis Corinth (1858–1925), was a key figure of German modernist art. Active since 1892 in the Munich Secession, in 1899 Corinth participated in the first exhibition of the Berlin Secession, of which Liebermann was President. That same year he painted Dr Mainzer’s portrait, also in Berlin, and shortly afterwards he relocated permanently to the capital. Corinth’s arrival in Berlin at the turn-of-the-century is widely seen as the moment when that city superseded Munich as the principal locus of avant-garde art in Germany. In time Corinth would assume the Presidency of the Secession in succession to Liebermann.

Ferdinand Mainzer was one of the most fascinating cultural figures in Berlin circa 1900. A German-Jewish gynaecologist, he was also an historian and writer – his Life of Julius Caesar was highly regarded - and a member of avant-garde circles. As has been noted, he turned to writing history because an injury to his hand meant he could not pursue his surgical interests. Mainzer’s biography of Caesar was translated into English and French, and is said to have inspired (among other works) the American playwright and novelist Thornton Wilder’s The Ides of March (first published in 1948).

It was no accident that Mainzer was among the first people Corinth met when he joined the Berlin Secession, nor that the doctor should commission his portrait from the brash artist from Munich whom everyone was talking about. Mainzer’s wife, Gertrude, was a pupil of Corinth’s old friend Walter Leistikow.

The Portrait of Dr Ferdinand Mainzer is a key transitional work in Corinth’s career, painted in the Impressionist style influenced by his mentor Liebermann but already exhibiting – see the sombre palette and bravura paint handling – intimations of the Expressionism that would come to the fore in his art in the following decade. Corinth immediately captures sophistication, wit, perhaps a touch of superciliousness, in Mainzer’s ultra-refined personality, as the doctor leans back in his chair to peer sceptically at the artist through pince-nez. There is a wonderful play between the sitter’s raised eyebrows and his perfectly manicured and twirled moustache. According to Mainzer family lore, the two quickly became, and long remained, friends.

Mainzer’s later life was only more surprising. In the 1930s, through his friendship with the charismatic Jesuit priest, Friedrich Erxleben, he became active in the so-called Solf Circle, a Roman Catholic group fiercely – and at considerable danger to themselves – opposed to Hitler and Nazi rule. Mainzer and his family fled Berlin with the help of Circle members, as the SS closed in (betrayed by a Gestapo infiltrator, most remaining members of the Circle were executed in 1944). The Mainzer family came first to London. Mainzer himself, together with his wife, soon moved on to America where he died in exile in Los Angeles in 1943, amidst its extraordinary expatriate German / Austrian intellectual community - Adorno, Mann, Reinhardt, Schoenberg – and where he is buried.