Laura Robson achieved her 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.
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 down.
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 level.
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.
"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 - they meet in round two 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 went on to claim 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."