Webpage created: July 14, 2017.
Webpage updated: July 14, 2017
During the twelfth century it became common for newly created boroughs to have the concession of forming a merchant gild/guild for the regulation of trade and commerce. As towns were created as a trading community it was natural that the members of the town council and the guilds should be one and the same men. This practice started, of course, in London and only slowly spread westwards to Plymouth.
In fact the first mention of a Merchant Guild -- or Guild Merchant, as it seems to have been called in Old Plymouth -- was in the Charter dated July 25th 1440 that His Majesty King Henry VI issued to Plymouth following their Act of Incorporation the previous year. Worth suggests that it was in the management of this Guild, by twelve Aldermen and twenty-four 'Common Councilmen' that lies the origin of the borough council formation.
Nobody had a right to trade in the town unless he was a freeman. Worth relates that in 1474-75 an order was made by the Corporation of Plymouth that: 'no man should be free of the Corporation unless he were a whole or half brother of Our Lady and Saint George's Guild'. It cost money to join the Guild: 12 pence a quarter for whole brothers, 6 pence for half brothers, 8 pence per year for the common councilmen and 12 pence per annum for the twelve Aldermen. This was sometimes known as the Freemen's Guild.
In 1479-80 a charter was granted to the tailors of the borough who were required to make a pageant annually on Corpus Christi Day. They became known as the Corpus Christi Guild. 
Of course the guild members needed to have somewhere to hold their meetings and gather for special occasions and hence the Guild Hall was born.