In Biggles Takes a Hand, the gang of professional assassins led by Ludwig Karkoff stayed at the Cosmolite Hotel on Cromwell Road, Kensington, after arriving in Britain on the trail of Frau Roth and her family. Von Stalhein told Biggles where the gang was staying after he had spotted them dining at the Adlon Restaurant and had followed them to their hotel.
The Cosmolite Hotel is fictional but Cromwell Road has many small hotels of the inexpensive, low profile type which a gang like Karkoff's might have chosen.