A pair of practice leaders at Gibson, Dunn & Crutcher are leaving the firm to take on two notable in-house legal roles.

A. Stephen Gillespie, co-chair of Gibson, Dunn's global finance practice in London, has joined Luxembourg-based investment firm LetterOne Holdings SA as general counsel. Meanwhile, national security practice chair Caroline Krass, who joined Gibson Dunn a year ago in Washington, D.C., after serving as general counsel at the Central Intelligence Agency, is headed to American International Group Inc. as deputy general counsel.

AIG announced Monday that Krass would also serve as its new senior vice president and general counsel for general insurance. Krass, who was the CIA's top lawyer from 2014 to 2017, will begin her role at the New York-based insurance giant in March.

Krass' legal career in the nation's capital included more than two years as acting assistant attorney general and as principal deputy assistant attorney general in the U.S. Department of Justice's Office of Legal Counsel. During the Obama administration, she served two years as special counsel to the president for national security affairs and as associate White House counsel, as well as two years as a deputy legal adviser to the White House's National Security Council. Krass was also a senior national security lawyer in the second administration of President George W. Bush.

Krass will report directly to Peter Zaffino, AIG's CEO for general insurance, and Lucy Fato, who last year was hired as AIG's new general counsel. As general counsel for general insurance, Krass will be responsible for the general insurance unit of AIG's massive global legal department.

“I am excited to be joining Peter and Lucy and the rest of the dynamic leadership team that is being formed at AIG, particularly in general insurance,” Krass said in a statement. “Insurance plays a critical role across the globe helping to mitigate and respond to risk, and I look forward to building upon my experience to help position AIG for long-term success at this pivotal time.”

A graduate of Yale Law School, Krass serves as an adviser to the U.S. Intelligence Community. Outside of Gibson Dunn, where she headed the firm's national security team, Krass is also a member of the American Bar Association Standing Committee on Law and National Security and the advisory board of the Georgetown University Law Center's Cybersecurity Law Institute.

As for Gillespie, he leaves Gibson Dunn a little more than three years after joining the firm from Kirkland & Ellis, a move that marked his now former firm's push into transactional finance and corporate work in London. Gillespie had previously spent eight years in Kirkland's European debt finance practice, and before that served as global co-head of banking at Allen & Overy.

At the time of his hire, Gillespie joined a run of high-profile additions for Gibson Dunn in London led by ex-Ashurst partners Nigel Stacey, Jonathan Earle and Mark Sperotto, who made the move with former Ashurst senior partner and London co-head Charlie Geffen.

More recent additions by Gibson Dunn in London include Serious Fraud Office prosecutor and case controller Sacha Harber-Kelly and two partners from Mayer Brown's London office, including the latter's former global co-head of corporate and securities Jeremy Kenley.

London co-chair Charlie Geffen told London-based Legal Week last summer that Gibson Dunn was still in growth mode in Europe, where the firm opened an office last year in Frankfurt, highlighting financial regulatory and competition as areas in which it wants to invest on the continent and in the U.K.

LetterOne, which is controlled by Russian billionaire Mikhail Fridman, was founded in 2013. It focuses its investments on the energy, health, retail, technology and telecommunications sectors, investing through four different brands, with liquidity managed by L1 Treasury.