According to Wikipedia (and they should know!), Castle Drogo is a country house near Drewsteignton, Devon, England. It was built in the 1910s and 1920s for Julius Drewe (businessman and founder of the Home and Colonial Stores) to designs by architect Edwin Lutyens, and is a Grade I listed building. Castle Drogo was the last castle to be built in England, and probably the last private house in the country to be built entirely of granite.
I just love Lutyens, Devon, and the West Country, and the idea of building a medieval castle in the 20th Century, is just so bizarre!