When David Leuschen split off from Goldman Sachs to co-found Riverstone in 2000, he had been with the bank for 23 years.

Inevitably, he had assumed some of the trappings associated with working at one of Wall Street’s most respected firms, but the cowboy in this Montana native remained.

When he is not doing business in New York, Mr Leuschen spends much of his time at his 200,000-acre Montana ranch just outside Yellowstone National Park, looking after his 2,000 cattle.

In season, he hunts elk, mountain goats and bighorn sheep on his ranch, as well as breeding and training “cutting” horses, which separate a cow from the herd.

Ever the entrepreneur, Mr Leuschen sells his beef to local steakhouses, while he has set up a second business, Switchback Outfitters, which leads hunting expeditions on horseback.

Mr Leuschen, a co-founder and senior managing partner at Riverstone, joined Goldman Sachs in 1977, co-founding and running its global energy and power group in 1985 and becoming a partner a year later. He received a degree from Dartmouth and an MBA from Dartmouth’s Amos Tuck School of Business.

He is understood to have approached Lord Browne of Madingley shortly after his departure in May. Mr Leuschen knows Lord Browne from his time at Goldman Sachs, where the former BP chief executive used to sit on the board.

Mr Leuschen also met Riverstone’s other co-founder, Pierre Lapeyre Jr, during his time at Goldman Sachs.

Mr Lapeyre worked at the Wall Street firm for 14 years, focusing on energy and power.

During his time at Goldman Sachs, Mr Lapeyre led the group’s coverage of Asian energy companies and worked at locating and executing energy investments for the firm’s private equity arm. He received a degree in finance and economics from the University of Kentucky and an MBA from the University of North Carolina.

Mr Lapeyre worked with some of America’s biggest energy companies during his time at Goldman Sachs, including Kinder Morgan, the gas pipeline business, and Unocal, the Californian oil company that is now part of Chevron. He serves on a variety of boards, such as Frontier Drilling, a drilling company serving the oil industry.