Dr Isobel Muir from the National Gallery has kindly supplied some text from a book with a description of life at Everleigh House in 1857.
The author of the book was Robert Selby HENREY (1901 – 1982). ‘A Century Between’ was published in 1937, and concerns his family (The Fitzroys). The relevant pages are 134-136.
The pages describe the activities of the Fitzroy children (Blanche and Arthur), whose parents were Hon. Henry Fitzroy (MP) and Hannah Mayer Rothschild, while they lived at Everleigh (at weekends).
The family lived at Everleigh in 1857, but their son Arthur died only a year later, of complications from a riding accident he had sustained 10 years before.
That is why only Blanche rode Salisbury Plain with her father in the description in this book.