Laura Robson achieved a first victory over a player ranked inside the world's top five by beating world number four Agnieska Radwanska at the Madrid Open.
The 19-year-old beat Radwanska, last year's Wimbledon finalist, 6-3 6-1 to progress to the third round.
Robson had endured a torrid few months, suffering a sixth first-round defeat of the year at last week's Portugal Open.
But the Briton was ruthless in Madrid, returning brilliantly to secure one of the finest wins of her career.
How nice to see Laura Robson smiling
again! Barring some good wins in
Australia it's been a barren year with
several morale-sapping deciding set
defeats, so this was much needed and
well deserved as she finds her feet on
clay in the build up to Roland Garros.
She returned superbly - Radwanska
unable to deal with the early pressure
in rallies - and importantly kept her foot
The Pole tried to use the drop shot
more in the second set, with a little
early success, but failed to win any of
her last five service games as Robson
sprinted through to one of her most
clinical and satisfying victories at this
"I'm really happy with how I played today and I went on the court with a clear game plan," Robson told BBC Radio 5 live.
"I've practised with her a couple of times so I knew what her strengths and weaknesses were."
Robson, ranked 41 in the world, will play either Ana Ivanovic or qualifier Chanelle Scheepers - who play their second round match on Tuesday - in the next round.
The teenager went toe-to-toe with Radwanska until she broke the Pole in the eighth game of the first set when the 24-year-old netted to give the Londoner a 5-3 lead.
Robson served for the set and quickly stamped her authority on the match by breaking her opponent in the first game of the second set.
Radwanska's riposte was immediate, breaking Robson in the second game, but Robson then secured a third successive break of serve and held to eke a 3-1 lead.
The Olympic doubles silver medallist was breaking the Pole with ease and forced Radwanska to serve to stay in the match which she was unable to do as Robson claimed her fifth break to wrap up victory in one hour and 13 minutes.
"I'm happy with my returns and a lot happier with my serves as well," added Robson.
"It's definitely great to beat a top 10 player, especially on clay. It's a very exciting day for me."