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The No.6 seed from Denmark came from a break down in the first set to claim it in a tiebreak on his fourth set point, and pulled clear in the second set after Alcaraz, who was on a nine-match winning streak, took a medical timeout.

“It means the world, it was such a great match,” Rune said after winning his fifth title on the ATP Tour and third on clay.

“In the beginning, I was a little bit stressed, because Carlos obviously plays big-time tennis. I had to breathe a lot and find my rhythm. After he broke me, I got more into the match and played my tennis. The first set was a big battle, it was super important to win it and gain the momentum. I’m so proud of myself.”

Rune also staved off four break points in the second set before pulling away to win it after Alcaraz twice required treatment on his upper right leg.

Rune, 21, beat defending champion Casper Ruud in the quarter-finals and showed why he's one of the Tour's brightest young stars, beating  an 18-time ATP Tour title winner in Alcaraz.

“When I got broken in the first set, I thought to myself that I don’t need to hit every shot on the line,” Rune said.

“So I [asked] myself, ‘What did Novak do when he beat him?’ I played it in my mind, the Olympics final, and tried to play that style, making a lot of balls. I’m very happy with how I stayed composed when it mattered, and I was really brave.”

Rune had already ensured a return to the world's top 10 by reaching the final and is now No.9 on the rankings.

Alcaraz was aiming to hold his No.2 spot, but has coughed it up to Alexander Zverev, who won the BMW Open title in Munich to reclaim that spot, but the Spaniard was gracious in defeat.

“Congratulations Holger on an amazing week,” Alcaraz said to Rune during the trophy ceremony.

“Coming from Monte-Carlo, [where] you had to retire [because of food poisoning]. Coming here and showing a great effort to make the people enjoy watching tennis, I appreciate that.

"We’ve been seeing each other since [we were] 12 years old. Time flies. I’m really happy to see us in this position, how far we’ve [come]. Keep going.”