Johanna Konta’s royal seal of approval from legend Billie Jean King

Johanna Konta during her French Open quarter-final win over Sloane Stephens. Picture: Jean-Francois Badias/AP

Having never before won a main draw match at Roland Garros, the British No 1 goes into tomorrow’s semi-final against Marketa Vondrousova as the favourite.

She is the bookies’ favourite, the logical favourite and the pundits’ favourite. And the pundit-in-chief Billie Jean King says she has never seen Konta play as well as she has these past couple of weeks

King, who won 39 grand slam singles and doubles titles in her career, said: “She’s really concentrating well and she’s hitting so big.

“Her serve’s big, her groundstrokes are big. She’s totally focused right now. Konta is playing the best I’ve probably ever seen her play except for when she had that run at Wimbledon. But I think she’s actually better now.

“I think her concentration is better day in and day out. I feel like some days she gets like too hyped up but she seems to be very calm right now, added King, pictured. “Konta, I can tell, she’s had a lot of therapy and I think it’s helped her.

“She’s quite clear now in her thoughts in what she wants  to do and she just keeps improving.”

In the first 11 days of the tournament, Konta was always the underdog. Clay was commonly thought to be her Kryptonite and, until this year, she had only won seven matches on the stuff in her life – and never once had she fot past the first round in Paris.

Pretty much everyone else in the draw had more experience of success at Roland Garros Paris than Konta.

But now she is into the last four, the third major semi-final of her career, and she is facing a 19-year-old from the Czech Republic whose best grand slam result until now had been a fourth round appearance at last year’s US Open.

Left-handed, ranked No 38 in the world and with a unique game of flair and variety, Vondrousova has been impressively consistent this year.

She has reached two finals, in Istanbul and Budapest, and got to the quarter-finals in Indian Wells, Miami and Rome (where she lost to Konta in three sets). But this is a grand slam semi-final. This is the last hurdle to clear before the trophy match. This is very, very different for the teenager.

Konta, though, has been here before and knows not to get too excited about anything.

She has a lot of work still to do and, while she is loving every minute of doing that work, she does not believe in the concept of favourites in any match-up.

“I think that’s what’s so exciting; that’s fun,” she said. “Vondrousova – I lost to her last year and I just beat her two weeks ago. So I go into the match 50-50.”

That approach may keep Konta on an even keel, but those who have watched her making her way through the draw for the loss of just one set, do not believe a word of it. Vondrousova is good but Konta has been a revelation.

“She’s a player who doesn’t miss much,” said Patrick Mouratoglou, the coach to Serena Williams. “She’s intense without missing. She attacks from the baseline but without missing. She imposes a high rhythm on the rallies. This can pay for sure on clay.”

“I think her number one quality is her mentality. She’s a fighter. She’s very intense in everything she’s doing. She has the same kind of mentality and tennis as Azarenka. She’s not someone who hits a lot of winners but she imposes a really high rhythm with a lot of intensity and power.”

What has surprised everyone is the relaxed, calm attitude Konta has to her new vein of form. She now “accepts” everything that happens to her on court.

She fluffs a shot, she accepts it and moves on; the pressure is mounting as she gets nearer to the final, she accepts it and enjoys the business of competing; she wins a match, she accepts it, enjoys it momentarily and then moves on.

“Acceptance has been a part of my vocabulary and part of my thought process for many years now,” Konta added.

“It definitely just got reignited, strengthened and more relevant in the last maybe year and a half or so, to practise acceptance that it’s not under your control or it is just part  of the situation you find yourself in.”