Invitation to the Waltz is a 1935 British historical musical film directed by Paul Merzbach and starring Lilian Harvey, Wendy Toye and Carl Esmond.
The visiting Duke of Wuerttemberg becomes fascinated with her and engages her to perform at the state operate house in his capital of Stuttgart, hoping also to make her his mistress.
The British authorities encourage Jenny to go to Stuttgart and try to live extravagantly at the Duke's expense in the hope that a shortage of funds with compel him to renew his treaty against Napoleon.
However at the border she once again meets the handsome aide she had first encountered in London, who has been ordered to escort her, and who is hurt by the fact that she now appears to be the Duke's lover.
Having finally persuaded the Duke to sign the treaty with Britain, her plans to escape from the Duchy are wrecked when Napoleon invades and captures Stuttgart.