Duckhorn Wine Company has sold a controlling interest in the company to a financial investment firm with offices in Menlo Park and London.

The purchase price by GI Partners LLP was reported to be about $250 million.

The sale was the third change in ownership of a Napa Valley winery in two days. Stag’s Leap Wine Cellars was sold Monday to a joint venture partnership of Chateau Ste. Michelle Wine Company of Washington and Marchese Piero Antinori of Italy for a reported $185 million. The sale included the famed SLV and Fay vineyards. Also on Monday, E & J Gallo announced the purchase of William Hill Estate and the 145-acre Silverado Bench vineyard from Beam Wine Estates. No purchase price was announced.

Alex Ryan, president of Duckhorn Wine Company, said under the agreement GI Partners eventually will acquire all of the outstanding stock of Duckhorn.

“What’s great about this relationship is that they want to continue the growth of the three brands as we have done over the years,” Ryan said. No changes in operations are expected.

In mid-March, Ryan denied the company was for sale. At that time, he said the board of directors brought in a Swiss financial services company to look at long-term strategic options for the wine company and determine the best way to continue to build and grow the company.

Ryan said the board had sought outside financial advice two or three times in the past that resulted in the founding of Paraduxx in 1994 and Goldeneye six years later, after a decade of research.

Duckhorn Wine Company includes Duckhorn Vineyards, Paraduxx and Goldeneye, and several vineyards in Napa and Mendocino counties.

“The team at GI Partners shares our vision and commitment for producing excellent wines and we are thrilled to welcome them to the Duckhorn family,” said Dan Duckhorn, co-founder and CEO of Duckhorn. “This investment will help build upon our tradition of quality that began more than 30 years ago, and we look forward to continuing to strengthen our relationships with existing suppliers and customers.”

GI Partners founder and executive managing director Rick Magnuson said, “Dan and his management team are highly respected in the wine industry and GI Partners is dedicated to supporting them in their ongoing focus to make outstanding Napa and Anderson Valley wine.”

GI invests in a range of industries, including healthcare, real estate, lodging, logistics, media, financial services and technology.

Dan and Margaret Duckhorn co-founded the company in 1976 and its first vintage was two years later when they made 800 cases of cabernet sauvignon and 800 of merlot.

Jack Heeger contributed to this report.