Hereditary peers form part of the peerage in the United Kingdom. There are over eight hundred peers who hold titles that may be inherited. Formerly, most of them were entitled to sit in the House of Lords, but since the House of Lords Act 1999 was passed, only ninety-two are permitted to do so, unless they are also a life peer. Peers are called to the House of Lords with a writ of summons.
A hereditary title is not necessarily a title of the peerage. For instance, baronets and baronetesses may pass on their titles, but they are not peers. Conversely, the holder of a non-hereditary title may belong to the peerage, as with life peers. Peerages may be created by means of letters patent, but the granting of new hereditary peerages has dwindled, with only six having been created since 1965, mostly for members of the Royal family.
The hereditary peerage, as it now exists, combines several different English institutions with analogous ones from Scotland and Ireland.
English Earls are an Anglo-Saxon institution. Around 1014, England was divided into shires or counties, largely to defend against the Danes; each shire was led by a local great man, called an earl; the same man could be earl of several shires. When the Normans conquered England, they continued to appoint earls, but not for all counties; the administrative head of the county became the sheriff. Earldoms began as offices, with a perquisite of a share of the legal fees in the county; they gradually became honours, with a stipend of £20 a year. Like most feudal offices, earldoms were inherited, but the kings frequently asked earls to resign or exchange earldoms. Usually there were few Earls in England, and they were men of great wealth in the shire from which they held title, or an adjacent one, but it depended on circumstances: during the civil war between Stephen and the Empress Matilda, nine Earls were created in three years.