"the Queen might be assaulted while I was strolling by Buckingham Palace"

Buckingham Palace
Creative Commons AttributionBuckingham Palace - Credit: Francesco Gasparetti, Flickr


As noted in bookmark, p.205, the role of guardsmen was (and is) to protect the Sovereign and her properties.

Buckingham Palace Guard
Creative Commons Attribution Share AlikeBuckingham Palace Guard - Credit: geraldford, Flickr
In London the guardsmen are responsible for the security of Buckingham Palace, St. James's Palace, and the Tower of London