During the bath tub scene, Marlene Dietrich slipped on a bar of soap falling naked and spreadeagled before cast and crew. Ever the professional, she picked herself up, laughed and continued shooting.
During the shooting Robert Donat had a severe attack of asthma and the film was delayed for almost a month. The producers wanted to replace him but Marlene Dietrich refused.
The poem quoted by Fothergill aka Ouronov is 'Prospice' by Robert Browning. The one quoted by the Countess is 'I have outlasted all desire' (1821) by Alexander Pushkin.