Mayor
1999 saw the creation by referendum of the post of a directly elected mayor for London, heading a Greater London Authority. Elections for mayor took place in the following year, which saw Ken Livingstone elected as mayor for five years.
The local government act, 2000, provides for a similar mechanism at a borough level. If a petition is presented with enough signatories, the local council are required to hold a referendum, as to whether the borough should have a directly elected mayor. The directly elected mayor replaces the civic mayor, a councillor who is appointed to the post by the borough council.
See this for the general arguments for and against.
Ealing held just such a referendum on the 12th December, 2002. The outcome was a "No" to a directly elected mayor, but the turnout was only 9.8%. See http://www.ealing.gov.uk/council/elections/mayor+referendum.asp