From time to time Isabella Bird stayed with both the Bishop of Chester and the Bishop of Winchester, who, when in London, lived in Winchester House, St. James's Square. In 1852, probably in late autumn, she paid her cousins there a visit, and on her way met with an adventure, her action in which illustrates the rapidity and courage with which she faced the unforeseen.

She had taken a cab from the railway station, and while driving out of the gate received on her lap a small parcel of advertisements, which, as was usual then, was thrown in at the open window. Putting it on the seat in front of her, she noticed another parcel lying, evidently left by the former “fare.” She opened it, and found papers inside giving details of a plot to assassinate a member of the Cabinet at the approaching funeral of the Duke of Wellington. She had scarcely put them into her pocket, when she heard a voice stopping the cab, and a dark, foreign-looking man addressed her at the window. He asked if a parcel had been found in the cab. At once she handed to him the little bundle of advertisements, and after a minute's progress bade the driver hasten to the Home Office, where she insisted upon seeing the minister, in whose hands she placed the papers. So serious did the matter appear to the Home Office that, while she remained in Winchester House, a detective was posted there to guard her against the vengeance of those whose plans she had frustrated.