Will Jason Kyrwood (left) ever get to show his parents New York? It’s a fair question. In 2008, Kyrwood, a Davis Polk corporate partner, had just welcomed his mum and dad from Australia when he was called in to represent the Federal Reserve Bank of New York in the $85 billion rescue financing for American International Group Inc. He spent the next six days working round-the-clock on the credit facility and finished just in time to wave them goodbye.

Fast-forward to November 2013: Kyrwood’s parents once again made the 22-hour trip from Australia to New York, only for Kyrwood to disappear at short notice for a second time, this time for two weeks, to work on the financing of Verizon’s buyout of Vodafone Group Plc from their joint venture, Verizon Wireless. Who knows what will happen the next time they visit.

At $61 billion, the Verizon bank financing is by far the largest in history. The transaction was so large, in fact, that several of the banks had to obtain special waivers as the deal breached their internal lending limits. “The size is eye-popping,” says Kyrwood, who advised the banks on the deal. “They are the kind of numbers that, for the first time in my career, actually made me a little nervous.” (Verizon was advised by Debevoise & Plimpton.)

The transaction was complicated by the fact that the seller, Vodafone, a U.K.–registered company, wanted the financing to be structured according to similar “certainty of funds” rules that apply under the U.K. takeover code. This required Kyrwood, working alongside lawyers in Davis Polk’s London office, to help negotiate a full credit agreement before the deal was announced—a much more intensive process than a standard U.S. financing, which typically only requires a commitment letter and term sheet to be signed up front.

Thomas Cassin, head of the high-grade loan capital markets and origination business at JPMorgan Chase & Co., which alongside Morgan Stanley was lead underwriter on the financing, praised Kyrwood’s responsiveness and judgment. “He’s up there with a very small handful of partners that we would call for an undertaking like this,” Cassin says. “If another deal like this came up tomorrow, I wouldn’t hesitate to use Jason again.”

Alan Denenberg, meanwhile, concedes that the confidentiality requirements Twitter imposed prior to its IPO in November were “pretty extreme.” Denenberg, the head of Davis Polk’s Menlo Park, Calif., office and lead adviser to the underwriters on the microblogging site’s $2.1 billion offering, says that meetings of the dozen or so members of the deal team were held in secret in a small office above a car garage in San Francisco’s Mission District. “You could hear them changing tires beneath us,” Denenberg says. “It was about as off-site as you can get.”

The group was also not allowed to use Microsoft Outlook to schedule the meetings, for fear of the calendar items being visible to secretaries or colleagues, and they weren’t allowed to wear suits to the meetings or to use items featuring their firm’s logo, such as umbrellas, pens or letterhead. (The deal team included senior personnel from Twitter and its legal adviser, Wilson Sonsini Goodrich & Rosati; lead underwriter The Goldman Sachs Group Inc. and its lawyers at Davis Polk; and accounting firm PricewaterhouseCoopers.)

But for Denenberg and the underwriters, there was a bigger, less prosiac, challenge: finding a way to attach a value to a company that had not been focused on generating revenue. In fact, Twitter still has not turned a profit. The company brought in $422 million in the three quarters preceding the IPO, but posted a net loss of $134 million.

Denenberg worked with the bankers to devise nonfinancial metrics that would “tell a story,” as he puts it, and speak to the commercial potential of a site that has 230 million users and has spawned a verb (to “tweet”). They built the prospectus around data such as average revenue per timeline view and timeline views per monthly active user.

It worked: Twitter raised $2.1 billion from the offering, including the greenshoe, making it the second-largest U.S. Internet offering ever.

“Alan is really a fantastic lawyer,” says Nick Giovanni, a technology investment banking partner at Goldman Sachs, who also worked with Denenberg on the IPO of Yelp Inc. in 2012. “He is totally committed and engaged, and was very helpful in solving some pretty tricky issues creatively and collaboratively.”