The Hong Kong legal practice of accounting firm PricewaterhouseCoopers has recruited longtime Mayer Brown JSM partner Martin Robertson, the latest in a series of recent hires by the legal arms of the Big Four in the city.

Robertson, who joins PwC’s Hong Kong affiliated law practice, Tiang & Co., specializes in cross-border mergers and acquisitions.

Robertson had been a partner with Mayer Brown JSM’s legacy Hong Kong firm Johnson Stokes & Master since 2000, having first joined the firm five years earlier. In 2014, he was part of the team that advised Shanghai Fosun Pharmaceutical Group Co. Ltd. on its $46.3 million investment in dietary supplements manufacturer Nature’s Sunshine Products Inc.

His arrival comes on the heels of another recent big hire by PwC’s Hong Kong affiliated law practice. At the end of May, the firm hired Martyn Huckerby, a former King & Wood Mallesons international partner in Shanghai, as head of Asia Pacific competition law.

Hong Kong-based Tiang & Co. was launched last year by ex-King & Wood partner David Tiang. It is associated with the accounting firm’s Singaporean law practice, PwC Legal International, and cooperates with PwC China member firms Beijing Rui Bai Law Firm and Shanghai Xin Bai Law Firm.

The other Big Four auditor with a Hong Kong legal practice, EY, also recently expanded, hiring four lawyers from Troutman Sanders’ recently closed office in the city.