The Guilds and Livery Companies

  Since London's bigger advantage is a good location for the trade, the majority of the London's citizens were craftspeople and merchants. Since Saxon times they have started to organise themselves into groups called "Guilds". Soon they became a very influential part of the London society.
  What I've found really intresting is that people from the same Guild usually worked and lived very closely to eachother. As a result a lot of streets of London were named after Guilds that stationed there. For example Bread St - where bakers lived or Friday St - where fishmongers were making quite a good buisness selling fish on Friday when Catholics couldn't eat meat.
  As the time passed these naturally-made groups oficially became "Livery Companies".
The main role of these Guilds were to protect the quality and reputation of a trade and the whole company.
  Suprisingly for me The Livery Companies were very strict about how members of the Guild should behave. Some historicians even reckon that anyone who was found on laziness or spending too much time on worthless activities would be excluded from the company.
  Very often Livery Companies' members were very well positioned in the London community.
  Such an influential and important group needed a common meeting place. So in 1440 the construction of Guildhall was finished. It is one of very few buildings that are still stnading in the City after the Great Fire.
Suprise! Livery Companies still exist in The City of London :)

Source:

http://www.history.co.uk/study-topics/history-of-london/the-guilds-and-livery-companies