The Aldermanries of the City of London
The City is divided into twenty six different sections called Wards. Each has its own Warden, or Alderman, to take care of running of each Ward. The Wards were named as follows....Twenty five of the City Aldermen are elected for a term, which used to be their lifetime, but is now up until the retiring age of a Magistrate. The twenty sixth Alderman (Bridge Gate Ward) must be a former Lord Mayor, and must also have been a Sherrif of the City. This has come to be, due to the change of City juristiction of the ward. Southwark, which formed Bridge Gate Ward, was in ancient times, a part of the City. This is no longer the case, but the old tradition carries on.
The Aldermen also have the final vote on who is to be Lord Mayor of London for the next year. The Liverymen of the City elect two final candidates from the list of nominees, and the Aldermen choose from these. http://barryoneoff.co.uk/html/the_wards.html