The 30-year-old, a three-time winner on the Ladies European Tour, drained eight birdies on the Marquess' course at Woburn Golf Club.

The only blemish on her round was a bogey at the par-five 11th, but she recovered by making gains on the 14th, 15th and 16th.

"Obviously I’m really chuffed to get in at seven under," Buhai, aiming to win her first major championship, was reported as saying by the African News Agency.

"I hit a bit of a wobble in the middle of my round, and to finish with three birdies and come in strong – I had a goal when I saw the lead was six to get to seven, so I holed like a 30-footer on the 16th hole and that got me to seven, so very happy."

Buhai has a one-shot lead over Japan's Hinako Shibuno and the United States' Danielle Kang.

A further shot back are world number two Park Sung-hyun of South Korea, Thailand's Moriya Jutanugarn, America's Megan Khang and England's Charley Hull, who is bidding to win a first major title on her home course.

World number one Ko Jin-young of South Korea is three off the lead as she looks to become the fifth woman to win three majors in a single season. 

The 24-year-old captured the ANA Inspiration and Evian Championship for her first major triumphs.

Ko's round of 68 included four consecutive birdies from holes five to eight.

Despite recording a bogey at the 12th and a double bogey at the 14th, birdies at the 13th, 15th and 18th capped off a good day's work.

England's Georgia Hall, the defending champion, is four behind on three under.