Cementing control, N.M. Rothschild & Sons merged seven years ago with the Paris-based bank behind the French branch of the family. The Swiss branch of the clan behind Edmond de Rothschild Suisse SA, meanwhile, aims to take the Geneva-based bank private as part of a plan to expand.

First known as Rothschild Investment Trust, RIT adopted its acronym upon Jacob’s exit from the U.K. business. Yet the omission of the Rothschild name hasn’t hindered its performance. Since debuting on the London Stock Exchange in 1988 in the wake of the deregulation of the city’s financial markets, the investment trust has grown more than 1,500%, eclipsing the market value of both the Swiss and French Rothschild banks.

“Over a range of asset classes and market cycles, there aren’t many who’ve delivered similar returns in the same period,” Cade said of Jacob Rothschild. “He really looks into the detail. If you’re putting forward a proposal to him, which I’ve done, you seriously have to know your stuff.”

A balanced investment ethos has attracted investors over that span, protecting shareholders in market downturns while delivering long-term growth.

“It’s very much a tortoise rather than a hare,” said Laith Khalaf, senior analyst at U.K. stockbroker Hargreaves Lansdown Plc, which holds an 8.6% stake in RIT. “It’s a good choice for a more conservative portfolio, or it could be used to form the foundation of a long-term portfolio.”

Jacob Rothschild’s reputation is also a powerful pull for investors. Educated at Eton College and University of Oxford, he became a partner in N.M. Rothschild & Sons four years after joining the family bank and ran its corporate-finance department. Along with RIT, he co-founded the FTSE 100 asset manager St. James’s Place Plc and formed part of a trio that joined forces three decades ago in a $21 billion aborted hostile takeover for British American Tobacco Plc.

“RIT is synonymous with Lord Rothschild,” said Alan Brierley, an analyst at Canaccord Genuity Group Inc. “It gives the investor exposure to an almost unparalleled network of contacts. It’s a very powerful brand.”

Even with at least $1 billion to his name, Jacob is far from becoming the richest member of the clan. Within the British branch alone, Nathan built a fortune that would be worth more than 10 billion pounds ($13 billion) today, according to “The Richest of the Rich,” by Philip Beresford and William D. Rubinstein.

The RIT stake from which Jacob and his family benefit rivals the Rothschild clan’s primary $840 million holding in their French bank. Evelyn de Rothschild, 87, sold his shares in the holding company for the family’s banking assets in 2007 for about 200 million euros ($223 million).

A chunk of Jacob Rothschild’s fortune stems from the inheritance he received after the death in 1988 of his distant cousin, Dorothy. Then worth 76 million pounds, it formed part of Britain’s largest will at the time, according to a 1990 article by the Spectator, a political magazine. It also gave him responsibility for running Waddesdon Manor, a 19th century country house built by one of his many wealthy ancestors -- Baron Ferdinand -- to display his art collection.