Berkshire (/ˈbɑrkʃər/ or /ˈbɑrkʃɪər/, abbreviated Berks) is a county of south east England, located to the west of London. It has also been known as the Royal County of Berkshire since at least the 19th century because of the presence of Windsor Castle and was recognised as such by the Queen in 1957 and letters patent issued in 1974.
More information on the Wikipedia page [1]