not be killed off in the series. Sam Reid will play a younger version of Harry. Nicola Walker returned as Ruth Evershed and Max Brown reprises his role as Dimitri Levendis. Brown said of his return to Spooks; "I couldn't wait to get back under the skin of Dimitri and see what new challenges he faced this year. He's a bit more senior now because he's been on the Grid for a year." Shazad Latif also reprised his role as Tariq Masood for the first two episodes, and Simon Russell Beale returned as Home Secretary William Towers. The series also introduced several new characters. Lara Pulver was cast as the new Chief of Section D, Erin Watts. Pulver described Erin as "young", "feisty", and has got "something to prove... but she has a maturity and a delicacy with the matters she's handling that makes her really good at her job." The character is also a single mother. The actress returned to London from Los Angeles to participate in other projects in the UK. When the Spooks casting directors heard of her arrival, they approached her. She was back in Los Angeles when she was told she won the part. Geoffrey Streatfeild was cast as Calum Reed, an information technology (IT) expert. Streatfeild researched his role before starting. The actor was a fan of Spooks and found it "weird to join a group of people when you know their characters." Jonathan Hyde and Alice Krige also had special guest roles in the series; Krige portrayed Elena, with Jenni Herzberg playing the younger version of Elena. Two main characters from the ninth series did not return for the tenth. Richard Armitage did not return as Lucas North. Firth has stated that Lucas "was always going to die" at the end of the ninth series. At the time the series was produced, Armitage was filming for The Hobbit film project. Also, Sophia Myles did not return as Beth Bailey as the character was decommissioned between the ninth and tenth series. Myles left the series as she wanted to pursue other projects in America. Matthew Macfadyen, who starred in the first three series as protagonist Tom Quinn, returned for a cameo appearance in the series finale. Production Crew Jonathan Brackley and Sam Vincent, who have been the head writers for the previous ninth series of Spooks, returned to their writing duties for the tenth