Catherine Standish’s explosive row with Jackson Lamb in Slow Horses season 3 means she will have a very different role in the upcoming series, but whatever path her story takes, I think I’ve figured out who is taking her place and it’s perfect. While Slow Horses is, at its heart, a spy story, the show’s biggest strength is its cast and characters. Jackson Lamb, River Cartwright, and every other member of Slough House have become integral to the show’s ongoing success. As such, replacing any team member is no easy task, with any change subject to intense scrutiny.

https://screenrant.com/slow-horses-season-4-standish-replacement-joanna-scanlon-perfect/