The fifth and last rank of the peerage is that of baron, which is ranked beneath duke, marquess, earl and viscount in precedence.
Baron literally meant 'man', being the king's tenant in chief (i.e. a land-holding nobleman). In the 13th century the barons were summoned by the monarch, by means of a Royal writ, to attend the Counsel or Parliament. Initially the conferral of this privilege did not imply that their successors would necessarily also be summoned to subsequent Parliaments. But by the reign of King Edward III (1327-77) it had become usual for successors of the more important barons to receive writs as a matter of course, in practice creating an hereditary dignity.
The first baron to be formally created by letters patent under the Great Seal, which represents the Sovereign's authority, was John Beauchamp de Holt, created Baron Kidderminster, by King Richard II in 1387. After about 1440 this became the normal method of creation of baronies.
In Scotland the equivalent of Barons in England are Lords of Parliament.
The rank of baron is easily the most populated in the peerage. There are currently 426 hereditary barons and lords of Parliament (not including courtesy baronies and lordships), and nine hereditary baronesses and ladies of Parliament in their own right.
The premier baron of England is Lord de Ros (created 1264), and the premier baron of Ireland is Lord Kingsale (created 1223), who lives in New Zealand. Since 1989, 24 baronies have become extinct, one (Kinnaird) is dormant or extinct, and another (Audley) is in abeyance.