The U.S. invasion of London continues. Am Law 100 law firms made further inroads into the fiercely competitive market in 2015, opening two new offices and bringing in a slew of high-profile laterals. But the outlook for 2016 and beyond is uncertain: The region’s already fragile economic recovery is under threat from a worrying rise in terrorism and the United Kingdom’s potential exit from the European Union.

The influx of Am Law 100 firms into London over the past two decades has irrevocably altered the legal landscape in the city. There are now at least 90 U.S.-based law firms with offices in the U.K. capital, collectively employing about 6,500 attorneys. And because they have higher profits per partner and more flexible compensation systems than most U.K. firms, they dominate the market for top laterals. At Linklaters, for example, real estate M&A head Matthew Elliott, competition partner Paula Riedel and private equity partner Roger Johnson all joined Kirkland & Ellis in 2015, while star restructuring partner David Ereira left for Paul Hastings earlier this year. (Magic Circle firms have responded to raids by modifying their locksteps; as of early April, Linklaters was reviewing its lockstep.)