The City of London was unique in evolving Common Hall as a separate electoral assembly for the choice of important municipal officers, including the Lord Mayor. At one time all freemen were entitled to attend but now only liverymen of the City Livery Companies or Guilds are present and only those liverymen of more than one year's standing are entitled to vote. No specific date can be supplied for the establishment of Common Hall, although its existence can be traced back to at least the 13th century. In 2008 Common Hall continues to meet on a regular basis.
Common Hall developed from an early assembly of citizens, termed a Congregation. Originally all freemen were entitled to attend such assemblies but apparently the assembly became too large for Guildhall. By the 13th century attendance depended on individual summons and constant orders were issued for enforcing the rule that only those summoned on the advice of the Mayor and Aldermen should attend. It became the practice in the 14th century to enlarge the administrative assembly for the purpose of elections by summoning further substantial citizens from the Wards. In 1422 and again in 1443 it was ordered that the election should be attended only by the Common Councilmen and other powerful and discreet citizens specially summoned, and on entry each person was called by name at the gate of the hall.
In 1467 the assembly was reinforced by the addition of the masters and wardens of the Livery Companies. This was the first step in the direction of organising the assembly on the basis of the guilds. It was followed in 1475 when the liverymen of the companies replaced men formerly summoned from the Wards. Although the ward men were probably also liverymen it must have had the practical result of broadening the assembly somewhat. It certainly had that effect in course of time for more and more companies were allowed the privilege of a livery. Thus the original right of all freemen to attend came to be limited to those freemen who were sufficiently substantial to assume, or later to be elected upon, the livery of their companies. This privilege of the liverymen was confirmed by Statute in 1725 which requires that electors shall be freemen and liverymen of at least one year's standing.
A Common Hall is summoned by precept from the Lord Mayor to the masters and wardens of the Livery Companies, requiring them to give notice to their liverymen to attend at Guildhall on a certain day. Another precept requires the attendance of the Beadle of each company at the entrance to Guildhall to prevent any other than liverymen from entering. The members of each company enter by a particular wicket [a fence of doorways] guarded by their Beadle, and the Common Cryer opens proceedings by directing all who are not liverymen to depart on pain of imprisonment. Common Hall is presided over by the Lord Mayor and cannot be held except by his direction and the business to be placed upon the summons is entirely under his control. His presence cannot be dispensed with except by the appointment in writing under his hand and seal of a locum tenens. On Midsummer Day, 24 June, the liverymen meet to elect two Sheriffs, two Bridge Masters, four Aleconners and six Auditors of the Chamber and Bridge House Accounts. Following the elections, the Livery Committee is appointed in accordance with the constitution and terms of reference approved in Common Hall on 24 June 1942. The election of the Lord Mayor takes place at a Common Hall held on Michaelmas, 29 September. All the Aldermen of the City of London who have served the office of Sheriff, except those who have already served as Lord Mayor, are automatically in nomination. The liverymen select two persons for submission to the Court of Aldermen for the final choice of one of them as Lord Mayor, a practice established in 1406. Choice is made initially by show of hands, but a poll or ballot may be demanded.
From the 16th to the 19th centuries the liverymen exercised the right of electing the members of Parliament for the City of London, an exclusive privilege confirmed to them in 1725 by 'An Act for regulating Elections within the City of London, and for preserving the Peace, good order and Government of the said City'. The Reform Act of 1832, while giving votes to inhabitant householders and occupiers of the annual value of £10, preserved the rights of the liverymen provided the civic freedom was acquired by servitude, or patrimony derived from a father free by servitude, and the liverymen resided within 7 miles of the City of London (subsequently extended by Act of Parliament of 1867 to 25 miles. The Representation of the People Act 1918 abolished the right of the liverymen as such to exercise the parliamentary franchise in the City of London but permitted those who possessed a business premises qualification to be entered on a separate list of liverymen in the register of parliamentary electors, and to vote as liverymen at Guildhall. The Representation of the People Act 1948 abolished the business premises qualification and also abolished the parliamentary constituency of the City of London and united it with the City of Westminster to form one parliamentary constituency, the Cities of London and Westminster.