Byron Trott, Founder of BDT Capital Partners, in the lobby of the Wrigley BuildingBDT Capital Partners

When Warren Buffett’s Berkshire Hathaway bought 38.6% of the Pilot Flying J truck stop chain on Tuesday, it did so with the help of a firm you’ve probably never heard of: BDT Capital Partners. 

That’s by design. Despite having more than $12 billion in assets under management, the merchant bank doesn’t even have a public-facing website.

It does, however, have more than 150 employees spread out over four offices in Chicago, New York, London, and Frankfurt, who advise extremely wealthy clients with family-owned businesses.

The firm intentionally flies under the radar to court these billionaires — like Buffett, the Waltons, and the Webers, to name a few — who value privacy.

Byron D. Trott, a midwest native who founded BDT, still helms the company from its Chicago headquarters inside the historic Wrigley Building.

Here’s how Trott went from a small-town football player to an investment banker advising billionaires: