“It was her choice,” executive producer Richie Jackson says. “She wanted to move back to London and devote time to theatre work there.”
Best — who played Dr. Eleanor O’Hara, the onscreen confidante and co- worker of Edie Falco’s title character, since the launch of the Showtime dramedy in 2009 — actually relocated to her native UK prior to the start of the show’s current fifth season. However, producers managed to keep O’Hara around via a handful of pre-taped cameos. (On the show, O’Hara also relocated to London.)
Source: TVLine