Andy Murray will face Novak Djokovic with the ATP World Tour Finals title and year-end number one ranking at stake on Sunday.
The 35th meeting between the pair will also be the first time the season finale has ended with the number one spot on the line.
Murray replaced Djokovic as number one earlier this month, and the Briton is on a 23-match winning streak.
"I'm really privileged to be a part of history on Sunday," said the Serb.
Djokovic has won the last four titles in London and will overtake Murray with another win.