15.4 miles (24.8 km) west-northwest of Charing Cross, it is one of the major metropolitan centres identified in the London Plan.[2] Uxbridge historically formed part of the parish of Hillingdon in the county of Middlesex, and was a significant local commercial centre from an early time. As part of the suburban growth of London in the 20th century it expanded and increased in population, becoming a municipal borough in 1955, and has formed part of Greater London since 1965.