Among the works on show at the exhibition of German expressionists at the Holt festival, there are paintings by masters such as Klimt and Schiele. But one canvas among the masterpieces, a simple portrait by a little-known painter and academic being displayed for the first time, may stop visitors in their tracks – not for the deftness of the brushstrokes, or the vibrancy of the colours but for the deep gash across the neck of the subject. The 1920s painting of a Dutch woman in traditional costume is badly damaged, but its owners have no intention of repairing it before...