From the Wikipedia page 
A county in the South East of England, and one of the home counties. The county borders Greater London, Kent, East Sussex, West Sussex, Hampshire, Buckinghamshire, and Berkshire. The historic county town is Guildford. Surrey County Council sits at Kingston upon Thames, although this has been part of Greater London since 1965. The London boroughs of Lambeth, Wandsworth and Southwark were considered part of Surrey until 1889; and Croydon, Kingston, Merton, Sutton, Barnes and Richmond - all now reclassified as part of Greater London - were part of Surrey until 1965.