The 20-year-old beat Chang Kai-chen of Chinese Taipei 7-5, 5-7, 7-6 (7/4) to win the HP Open in Osaka in a final lasting three hours 11 minutes.

The victory puts Watson in the top 50 of the WTA singles rankings and makes her British Number One.

The last British winner of a singles title on the WTA tour was Sara Gomer in California in 1988.