The 17-year-old came from 3-1 down in the first set to beat her doubles partner, Russian Yana Buchina, 6-4 6-1. in the final at Flushing Meadows, New York.

On her way to the final, the 11th seed also defeated the World No 2 and this year’s Junior Wimbledon champion Noppawan Lertcheewakarn in the quarter-finals and Daria Gavrilova in the semi-finals.

Due to rain, both matches were played indoors on Saturday and Watson won both in straight sets.

The last British player to win a junior title was Andy Murray. Watson is the first to win the girls’ title.