PwC has agreed to an alliance with U.S. immigration specialist law firm Fragomen in one of the most significant examples to date of the Big Four joining forces with a law firm.

The alliance between PwC UK and Fragomen—which has more than 50 offices around the world and posted revenue of $577 million (£441 million) for 2017—will hand PwC a major foothold in the U.S. market, where the New York-based firm has 16 offices across all major financial centers.

The deal brings together two of the world's top providers in the immigration sphere and will see PwC and Fragomen team up to jointly pitch for work from multinational clients. Significantly, the relationship will also enable shared clients to draw on PwC's complementary services in tax, Social Security and global mobility consulting.

In a joint statement, the firms said the strategic alliance would see them collaborate and jointly market their immigration services, while also giving them “the ability to come together to provide integrated services to their respective clients.”

PwC's global immigration practice covers 170 countries, while the 550-lawyer Fragomen has offices in more than 25 countries outside the U.S., including an eight-partner London base.

Discussions over the alliance—which was announced to partners at both firms late last week—have been led by PwC legal markets leader and head of global immigration Julia Onslow-Cole, Fragomen chairman Austin Fragomen, PwC head of legal services Mike Bailey, and Fragomen international managing partner Lance Kaplan, while a governance committee has also been set up to oversee the relationship on both sides.

“Our global immigration practice covers more than 170 countries,” Onslow-Cole said. “Making our respective immigration teams available to clients, particularly in the U.S., will provide an even deeper level of local insight.”

“This alliance will also facilitate more strategic, global insights on the impact of government policies on both corporate immigration and mobility.”

The alliance has no connection to the legal operation PwC launched in Washington, D.C., last year. ILC Legal, which does not provide U.S. legal services, is staffed by a small team led by office managing partner Richard Edmundson.

Fragomen is well-known as one of the most gender-diverse international law firms, and for seven years has held the top spot on The National Law Journal's Women in Law Scorecard, which ranks the largest U.S. law firms by their percentages of female lawyers. In 2017, women made up 63 percent of its 553 lawyers and accounted for nearly half (44 percent) of its equity partners. The firm has had a London office since 2003, and in 2011 took on CMS Cameron McKenna's entire 15-lawyer immigration practice, led by partner Caron Pope.

“Immigration strategy and compliance has never been more important,” said Fragomen chair Austin Fragomen. “Clients seeking aggregated legal, tax and mobility services will get best-in-class services by working with Fragomen and PwC.

“Our immigration legal expertise, coupled with PwC's professional services offerings, will give clients an unparalleled opportunity to benefit from a unique collaboration that will help them better manage mobility and mitigate risk in a fast-changing compliance environment.”

PwC's legal operations brought in about £70 million ($92 million) in U.K. revenue during the 2017-18 financial year—a figure that would have put it only just outside the U.K. top 50.

The Big Four accounting firm now has about 350 fee earners in the U.K., offering advice in areas including immigration, cybersecurity and data protection, corporate reorganizations, disputes, employment, M&A, pensions, and technology.

The firm's legal services arm, which since October 2017 has been led by Ed Stacey, is no longer a distinct business unit after an integration process that means its lawyers now sit alongside their counterparts from the wider firm and report into PwC's leadership.

All of the Big Four accounting firms are making inroads into the legal market, and earlier this year Deloitte became the last of the quartet to receive an alternative business structure license enabling it to provide legal services.

The same month, Deloitte's U.K. arm agreed to an alliance with U.S. immigration firm Berry Appleman & Leiden, while also acquiring the firm's operations outside of its home country. In the U.S., Berry Appleman has 108 lawyers across eight offices.