Brockley Hill, Stanmore, on the outskirts of North London, England, rises to 136 metres (446 ft) above sea level. The road leading over it is also named Brockley Hill. The area is associated with the archaeological site called Sulloniacis. Its most prominent building is the Royal National Orthopaedic Hospital. In its present form the name dates from the 16th century; the earlier form was Brokhole(s): 'badger-holes', from the old English and Celtic word Brock. The sandy soil of the hill-top is more attractive to burrowing animals like badgers, than the heavy London clay of the surrounding areas.
Brockley Hill is the eastern arm of a long hill centred on Stanmore. The top of the hill is capped with "Stanmore Gravel", which is the remnant of a layer of gravel laid down by a river system pre-dating the Thames. Under the gravel are layers of sand, silt and clay about 15 metres thick known as the Claygate Beds. Below this is London Clay about 70 metres thick. This arrangement is typical of hills bounding the Thames Valley.