Short answers, pulled from the story.
Napoleon Bonaparte arrived at Longwood House on the 10th of December 1815 to begin his final exile. He lived there until his death on the 5th of May 1821 while holding the title of Emperor of the French.
The property known as Longwood House began its life as a farm owned by the East India Company. It served as a country residence for the Deputy-Governor of Saint Helena before Napoleon ever set foot on the island.
Reports from General Gourgaud reached London and influenced Lord Bathurst's perspective on safety protocols regarding relocation plans. The British government decided keeping Napoleon at Longwood was safer for preventing any potential escape attempts.
The French government purchased Longwood House along with the Valley of the Tomb for £7,100 in 1858. Ownership has remained under the control of the French Foreign Ministry since that transaction date.
Structural decay caused by termites threatened the building during the 1940s prompting serious consideration of demolition. Only the stone steps at the front remain as part of the original fabric from the early 19th century after restoration efforts.