US Open 2015: Johanna Konta plays the match of her life to win heated epic against Garbine Muguruza

It was the best win by a British woman anywhere since Laura Robson beat Li Na in the same tournament three years ago

Johanna Konta crowned the best run of her career with her finest victory here to reach the third round of a Grand Slam tournament for the first time. In energy-sapping heat and humidity the 24-year-old Briton won the longest women’s match at the US Open for 45 years to beat Garbine Muguruza, the Wimbledon runner-up, 7-6, 6-7, 6-2 after three hours and 23 minutes. It was the best win by a British woman anywhere since Laura Robson beat Li Na in this tournament three years ago.

Winning has become a habit for Konta, who has been in excellent form ever since qualifying for the French Open at the start of the summer. The world No 97, who next faces Germany’s Andrea Petkovic, has now won 15 matches in a row since Wimbledon and could soon take over from Heather Watson, the world No 61, as the highest-ranked Briton. She has already guaranteed herself a prize-money cheque for $120,200 (nearly £79,000), the biggest of her career.

Given the circumstances this was by some margin Konta’s biggest win. In her previous seven appearances in Grand Slam tournaments she had won only one match, having beaten Timea Babos on her debut here three years ago.

Although Muguruza has not had the best of times since her run to the Wimbledon final – she had not won a subsequent match until the first round here and recently parted from her coach – the 21-year-old Spaniard is one of the game’s most exciting young talents.

Konta, however, took the game to the world No 9 from the start, even if she was helped on occasions by Muguruza’s erratic ball-striking, which led her to 59 unforced errors compared with the Briton’s 34. Konta, who had 19 break points in the match, struck the ball cleanly throughout, built her points intelligently and, most impressively of all, showed great mental strength. There have been times in the past when nerves have got the better of Konta, but the work she has been doing with a mental coach since the end of last year is clearly paying off.

The conditions on Court 17 could hardly have been more testing, with the temperature climbing to 32C and the humidity at 45 per cent. The American Jack Sock was playing Ruben Bemelmans on another court at the same time and had to retire in the fourth set after suffering severe body cramps. “It was definitely hot out there,” Konta said. “I was really perspiring. I felt I dealt with it the best I could. I was hydrating. I was nibbling on a banana. I was doing what works for me.”

With both women chasing down shots into every corner and endeavouring to make their opponent play the extra ball, it was soon clear that the match would be a marathon. The first five games took nearly half an hour and the first set an hour and 20 minutes.

Konta broke serve in the seventh game on her seventh break point and failed to take two set points when Muguruza served at 4-5. The Briton was broken when she served for the set at 5-4 but kept her nerve in the ensuing tie-break, which she won 7-4.

In the second set it was Muguruza’s turn to fail to serve out when 5-4 ahead and in the second tie-break Konta’s mental resolve was tested to the full. With Muguruza leading 5-3, the Spaniard made a successful Hawk-Eye challenge against an “out” call. To Konta’s horror, the umpire, Carrie Hinueber, awarded the point to Muguruza, despite the Briton’s protests that the line judge’s call had affected her subsequent shot, which she failed to put in court.

Muguruza went on to win the set, but Konta came out as focused and determined as ever in the decider. The Briton won the first four games and this time served out for victory, Muguruza putting a forehand long on the first match point.

“I was very happy with how I was able to stay tough when I needed to and stay calm when I needed to,” Konta said. “Obviously, nothing is ever going to be perfect, so I’m just happy I was able to roll with the punches as they came.”

Petkovic, who has never played Konta, progressed with a 6-3, 7-4 victory over Elena Vesnina. Simona Halep, the world No 2, reached the third round by beating Kateryna Bondarenko 6-3, 6-4.