LionTree was the lead advisor to Liberty  on its bid for Virgin , which by any measure was a very big deal. Liberty-Virgin would be the second-largest M&A transaction since the financial crisis, only behind Dell’s (LBTYA) recently-announced $24.4 billion leveraged buyout, according to S&P Capital IQ. And if you exclude private equity deals, it would be the largest pure M&A transaction since Freeport McMoRan’s $26 billion acquisition of Phelps Dodge in February 2007.

LionTree, which had been working on the transaction for about five months, declined to comment on the Liberty deal.

The firm was founded by Aryeh Bourkoff, the former head of investment banking for the Americas at UBS .

Bourkoff, 40, was among many to leave UBS last spring, following a trading scandal, revenue declines and planned reductions. Even before Bourkoff had created a full plan for his new venture, he was joined as a partner by Ehren Stenzler, who had been co-head of M&A at UBS. The two men had worked together on several telecom, media, and technology deals including Comcast’s 2011 acquisition of 51% of NBC Universal.

Bourkoff made a name for himself as a media banker at UBS, where over the course of a 13-year career he amassed a powerful Rolodex of contacts and friends that spans the media and tech worlds.

During the most recent presidential race, he attended a small Obama fundraiser hosted by Harvey Weinstein, where he sat with Gwyneth Paltrow and Chris Martin (during a 2008 election cycle fundraiser for Obama, he sat next to Anna Wintour).

And Bourkoff hosts a low-key event in Deer Valley called Media Slopes, where a small group of rising executives from companies like Facebook (FB) and Google (GOOG) talk about how technology is changing the future of media between black diamond runs. Guests have included Strauss Zelnick, Reid Hastings of Netflix (NFLX), Liberty Media’s CEO Greg Maffei and YouTube content head Robert Kyncl.

Since it was founded in July, LionTree has advised on several smaller deals. Last summer, the Canada Pension Plan and private equity firm BC Partners bought a stake in Suddenlink Communications for $2 billion, with LionTree and Goldman Sachs advising Suddenlink. LionTree also advised Liberty Global and Searchlight Capital Partners on a $585 million acquisition of San Juan Cable, according to Dealogic.

In December, Bourkoff and LionTree advised Ryan Seacrest and the Seacrest Global Group when it bought a majority stake the advertising agency Civic Entertainment Group. Last month the firm worked with Jefferies to advise the private equity firm Rizvi Traverse Management on its deal for a majority stake in the music rights company SESAC for $600 million.

LionTree not only advises on deals, it plans to invest alongside clients using firm capital and money raised from high net worth individuals including Len Blavatnik, according to people close to the firm.