Steward of the Chiltern Hundreds

The Chiltern Hundreds was an ancient administrative area in Buckinghamshire, England, composed of three "hundreds" and lying partially within the Chiltern Hills. "Taking the Chiltern Hundreds" now refers to the legal procedure used to effect resignation from the British House of Commons. This is because the ancient office of Crown Steward for the area (in full Crown Steward and Bailiff of the three Chiltern Hundreds of Stoke, Desborough and Burnham), having been reduced to a mere sinecure by the 17th century, became the first to be used in this resignation procedure a century later. Other titles were also later used for the same purpose, but at present only the Chiltern Hundreds office and the Crown Steward and Bailiff of the Manor of Northstead are used.

A hundred was a traditional division of an English county that could raise one hundred fighting men for the Crown. The three Chiltern Hundreds were Stoke Hundred, Desborough Hundred, and Burnham Hundred. Despite their collective name only Desborough Hundred was located within the area defined by the Chiltern Hills in Buckinghamshire. The area had been Crown property as early as the 13th century.

Through the Saxon and early Norman periods the area was administered by an elder. But by the late Middle Ages the office holder was elected from among a hundred's notable landholding families. As the area was wild and notorious for outlaws, a steward and bailiff was appointed directly by the Crown (thus as a royal bailiwick it was a legal office answerable to the reigning monarch) to maintain law and order. However, by the end of the 16th century such positions had been depreciated by changes in local and Crown representations and roles - the government of Elizabeth I had established royal representatives (Justices of the Peace, Sheriffs, and Lords Lieutenant) in every county of England and Wales; they ensured that Royal commands and laws were obeyed. By the 17th century the office of steward and bailiff was reduced to just a title with no attached powers or duties.

...
Wikipedia