Clifford Chance investigations director Zoe Osborne has left the Magic Circle firm to join U.S. outfit Steptoe & Johnson, according to a person with knowledge of the move.

Osborne had been at CC for 13 years. She was part of the firm's team that advised oil services company Unaoil in 2016 when it was investigated by the U.K.'s Serious Fraud Office (SFO).

The investigation focused on claims that Unaoil paid multimillion-pound bribes to win contracts in the oil and gas industry.

Steptoe & Johnson's London base, which opened in 2001, has had a historical focus on investigatory work that often involves the SFO.

In 2013, it hired the SFO's joint head of bribery and corruption Patrick Rappo as a London-based partner in its white-collar criminal defence practice. Rappo left the firm last year to join DLA Piper.

Osborne becomes the latest lawyer to depart CC's investigations practice for a U.S. firm. Last January, white-collar star Judith Seddon left the Magic Circle firm to join Ropes & Gray.

Other firms to have boosted their investigatory prowess recently include Slaughter and May, which made a heavyweight hire last year with the addition of ex-SFO director David Green QC.

Green's hire followed months of speculation, with City white-collar partners debating whether it could cause possible conflicts issues.

Steptoe & Johnson did not respond to requests for comment.

CC declined to comment.