Andy Murray is finally world number one after Milos Raonic withdrew from their Paris Masters semifinal match.
The British tennis player needed to reach the final after current number one, Novak Djokovic lost to Marin Cilic in his quarterfinal game on Friday.
But injury problems to Raonic, causing him to withdraw from Saturday’s semifinal has buoyed Murray to the top spot.
Murray will be the first British singles player to hold top spot since computerised rankings began in 1973.
The Scot will play John Isner in Sunday’s final, after the American beat Cilic 6-4 6-3 in Saturday’s first semi-final.
Djokovic had topped the rankings for 122 weeks, and completed his career Grand Slam by beating Murray in the French Open final in June.
He will be officially announced as number one on Monday, when the rankings are revised.
Raonic, 25, had beaten France’s 11th seed Jo-Wilfried Tsonga 6-2 7-6 (7-4) to set up a repeat of July’s Wimbledon final on Saturday.
However, he said that he had felt a problem in his leg during the victory, which a scan revealed was a tear to his right quad.
“Yesterday at I believe 4-2 in the first set I began feeling something in my leg – I didn’t think too much of it at the time,” he said.
“This morning I had trouble waking up and getting out of bed.
“I had some tests and an MRI and they found I have a grade one tear in the right quad so I’m unfortunately not able to compete.”