Until 1844, many of the counties in England and Wales had exclaves (detached parts) entirely surrounded by other counties. Under the Counties (Detached Parts) Act 1844, many of these exclaves were absorbed by the counties within which they were located. The process was based on a schedule attached to the Parliamentary Boundaries Act 1832, drawn up by a boundary commission headed by the surveyor Thomas Drummond. Nevertheless, a number of exclaves remained; these were dealt with in a piecemeal manner over a period of decades.