British No 4 Katie Boulter claimed one of the best victories of her career against former US Open champion Sam Stosur to reach her first WTA Tour quarter-final at the Nature Valley Open in Nottingham.

The 21-year-old, ranked 156, has made significant strides in 2018 and powered to a 7-6 (8/6) 6-1 victory over Australian Stosur, the winner at Flushing Meadows in 2011.

Boulter will next face either top seed Ashleigh Barty or Duan Ying-ying of China.