CORRECTION: 9/13/13, 9:45 a.m. EDT. The Am Law Daily inaccurately reported the firm advising Twitter on its upcoming IPO, citing a letter from the company to the SEC that was filed on September 13, 2011, not September 11, 2013. Twitter's IPO filing is confidential. We regret the error. The headline has been corrected and new information has been added to the sixth, seventh, and eighth paragraphs of this story.

The much-anticipated initial public offering of social networking company Twitter was made official Thursday, along with those for Hilton Worldwide and the United Kingdom’s Royal Mail Holdings—all of which have enlisted the efforts of a handful of leading Am Law 100 and global firms.

The British government confirmed plans to undertake the country’s largest privatization in 20 years with an IPO for its Royal Mail service, while private equity giant The Blackstone Group officially filed its IPO prospectus for hotel operator Hilton, which it bought for $26 billion at the height of the buyout boom in 2007.

But it was the ubiquitous Twitter, with more than 200 million users around the world, which trumped both Blackstone and the Queen Mum by tweeting late Thursday the news that it had confidentially submitted paperwork to the SEC confirming its long-awaited IPO.

Twitter's estimated value is nearly $10 billion, and a stock float for the San Francisco–based microblogging service is among the most anticipated since Facebook’s $5 billion float last year. Fenwick & West handled Facebook’s controversial listing on Nasdaq, and the IPO generated $2.6 million in legal fees and expenses, according to SEC filings.

Fenwick has long served as Twitter's outside counsel, although the company's current legal advisers for its future IPO initially remained secret due to the confidential nature of the listing, as reported late Thursday by sibling publication The Recorder. Fenwick corporate partners Daniel Winnike and Theodore “Ted” Wang in Mountain View, California, are named in a letter Twitter filed with the SEC's division of corporate finance in September 2011. Wang’s Twitter feed touts his credentials as the company’s “first outside lawyer.”

Wang and Fenwick helped set up the company back in 2006, and the firm itself has been a Silicon Valley stalwart when it comes to advising technology companies and other start-ups backed by venture capital firms, perhaps best evidenced by its work representing Facebook last year, which The American Lawyer covered in detail in a May 2012 feature story. Wang and Winnike did not respond to requests for comment about Fenwick's work for Twitter.

It appears Wilson Sonsini Goodrich & Rosati, led by chairman Larry Sonsini, has landed the lead role advising Twitter on its upcoming IPO. Reuters reports that Sonsini confirmed his retention in an email Friday morning. Sonsini, whose firm advised Google on its high-profile IPO back in 2004, did not immediately respond to a request for comment by The Am Law Daily, nor did a Wilson Sonsini spokeswoman.

Twitter’s general counsel, Alexander Macgillivray, announced late last month that he would step down to make way for deputy general counsel and Wilson Sonsini alum Vijaya Gadde. Ironically enough, it was Fenwick’s Wang who The Recorder reports first recommended that Twitter hire Gadde several years ago. Gadde will now guide the company through its going-public process, presumably with Wilson Sonsini at her side.

The Recorder reported earlier this year on a reshuffling of the in-house legal ranks at Twitter, which was cofounded by Jack Dorsey, Noah Glass, Christopher “Biz” Stone, and Evan Williams. (Glass was pushed out of the company shortly after its inception.)

In June, former Twitter legal director Nicole Wong resigned to become deputy U.S. chief technology officer for the White House. Twitter then launched its first political action committee and hired its first federal lobbyist in William Carty in August, according to sibling publication The National Law Journal.

While Twitter tweets away, New York–based Blackstone is getting ready to cash out of its investment in Hilton, in what will be the second big private equity exit this week after the $6 billion sale of luxury retailer Neiman Marcus.

Simpson Thacher & Bartlett corporate partner Joshua Ford Bonnie is advising McLean, Virginia–based Hilton as it prepares an IPO that could raise up to $1.25 billion. The firm represented Blackstone on its $26 billion buy in 2007 of one of the world’s largest hoteliers. Simpson also handled a $4 billion debt restructuring in 2010 for Hilton, which owns more than 4,000 hotels around the world, as well as Blackstone's $950 million acquisition of the Mint hotel chain in 2011.

The American Lawyer named Bonnie a Dealmaker of the Year in 2008 for his role counseling Blackstone on its own IPO, which included crafting novel tax-saving structures that avoided IRS and SEC scrutiny. Fees and expenses for attorneys related to the Blackstone IPO were $15 million, according to an SEC filing at the time, but fees linked to the looming IPO for Hilton are not yet available.

Former Simpson M&A chair John Finley, an American Lawyer Dealmaker of the Year in 2009, left the firm the following year to become Blackstone's chief legal officer. Finley succeeded former Simpson corporate partner Robert Friedman, who had joined Blackstone in 1999 and remains a senior managing director at the private equity firm.

An SEC filing by Hilton does state that an investment vehicle composed of select Simpson partners and their families owns less than a 1 percent interest in the capital of Blackstone-affiliated funds.

Davis Polk & Wardwell capital markets cohead Michael Kaplan and corporate partner John Meade are advising underwriters for the Hilton IPO led by Bank of America/Merrill Lynch, Deutsche Bank, Goldman Sachs, and Morgan Stanley.

Kristin Campbell has served as Hilton’s general counsel since 2011. Last year Sutherland Asbill & Brennan hired former Hilton assistant general counsel Mark Robertson as a partner in Washington, D.C. Robertson is now a partner at Larkin Hoffman Daly & Lindgren.

Lastly, Magic Circle firms Freshfields Bruckhaus Deringer, Linklaters, and Slaughter and May have landed roles on a proposed IPO for the London-based Royal Mail, according to British publication The Lawyer. Freshfields has been advising the British government for more than a year on a restructuring of the Royal Mail, whose IPO could see some of the state-owned postal service's 176,000 employees get shares for free.

Legal Week reported last year that Slaughter and May has been advising the Royal Mail, with Linklaters stepping in this summer to represent banks underwriting the proposed public listing.