Middlesex (Middx) is an ancient county in southeast England, preceded by the Kingdom of Essex, established in the Anglo-Saxon system from the territory of the Middle Saxons It was encompassed in 1965 within the ceremonial county of Greater London, with small sections in other neighboring ceremonial counties The historic county included land from north of the River Thames, 17 miles west to 3 miles east of the City of London, with the rivers Colne and Lea; a ridge of hills were the other boundaries. The largely low-lying county, dominated by clay in its north and alluvium on gravel in its south, was the second smallest county by area in England in 1831