His father was from a family of Prussian barons and owned an estate called in Daudžgiriai [lt], while his mother was a Cossack from the Crimea.

[1][2] In the 1920s, de Ropp went to Berlin as a representative of the Bristol Aeroplane Company and became an associate of Alfred Rosenberg, a fellow Baltic German and a Nazi enthusiast.

De Ropp had contacts with a powerful segment of the British upper class which favoured appeasement, known as the "Cliveden Set", and also with a member of the royal family, the Duke of Kent.

Hitler used him as a confidential consultant on British affairs and outlined to him frankly his grandiose plans, described by one author as "a trust no other foreigner enjoyed to this extent".

While the Nazis considered de Ropp one of their agents in England, his standing helped facilitate a visit by Winterbotham to Germany in 1934.