Lauded Reuters general counsel Rosemary Martin has been overlooked for the top post-merger legal job at Thomson-Reuters in favour of Thomson's legal director, Deirdre Stanley.

Martin, who joined Reuters from Mayer Brown as deputy company secretary in 1997, is one of the best-known in-house lawyers in the UK. She has been the director of Reuters' charitable arm, the Reuters Foundation, since 2002 as well as being vice chair of in-house lobbying group, the GC100.

In 2005 Martin instituted Reuters' first-ever formal review of outside legal advisers, naming nine firms including Freshfields Bruckhaus Deringer, Ashurst, Clifford Chance, Burges Salmon, Weil Gotshal & Manges and Mayer Brown on the panel.

Principal Reuters corporate adviser Slaughter and May is leading a raft of firms advising the media giant on the £8.7bn merger, while Allen & Overy won the mandate to act for Thomson.

Stanley, a former corporate lawyer at Cravath Swaine & Moore, has been at Canada-based Thomson since 2002 and was previously deputy general counsel at legacy tech company USA Networks (now USA Interactive).

Reuters' chief executive Tom Glocer is set to become chief executive of the combined business and will lead an executive team comprising senior figures from both companies.

Martin will remain in her current role until the completion of the merger early next year, when Thomson-Reuters will become the world's biggest news and financial data company. It is not yet known whether she will take on a new role at the merged company.

Reuters operates across 94 countries and has a global legal spend of £12m. Thomson has annual revenues of $6.6bn (£3.3bn) and 38,000 employees.