What is "portpool"

Portpool was a manor or soke in the district of Holborn, London. It is not recorded in the Domesday Book but references to it occur from the 12th century onwards. For many years it was owned by the Dean and Chapter of St Paul's Cathedral, who let it out to the Grey family. The manor house of Portpool subsequently became known as Gray's Inn, acquiring a reputation for the teaching of law.