alternatehistory.com

2000-2008: Ken Livingstone (Labour)
2000: (Ran as Independent) def - Steven Norris (Conservative), Michael Oliver, Lord Mayor of London (The City), Susan Kramer (Liberal Democrat)
2004: (Alliance: Green/Workers of London) def - Steven Norris (Conservative/The City/Civic Concern), Paddy Ashdown (Liberal Democrat), Gerard Batten (UKIP/Anti-Assembly)
2008-2012: Karen Brady (Conservative)
2008: (Alliance: The City/Civic Concern) def - Ken Livingstone (Labour/Workers of London), Brian Paddick (Liberal Democrat), Gerard Batten (Independent/Anti-Assembly), Nigel Farage (UKIP)
2012-2016: Karen Brady (Independent)
2012: (Alliance: Conservative/The City/Civic Concern) def - Alan Sugar (Labour), Ken Livingstone (Left.UK), Sian Berry (Green), Simon Hughes (Liberal Democrat), Bob Crow (Workers of London), [Boris Johnson withdrew to endorse Brady]
2016-0000: Jeremy Corbyn (Labour)
2016: (Alliance: Left.UK/Left Green/Women's Equality) def - Zac Goldsmith (Conservative/The City/UKIP/Civic Concern/Right Green), Tom Brake (Liberal Democrat)

Based on that list @shiftygiant posted the other day, I wanted to create a scenario where London uses "Fusion" voting for its elections like New York. May add notes later.