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Sacha Dhawan returns to Doctor Who in this weekend's special, "The Power of the Doctor," which airs Sunday at 8pm EST on BBC America. Ahead of his latest appearance as the Time lord's longtime rival, The Master, here's a reminder of some of his most memorable roles.
1. The History Boys (2006)
Alan Bennett's Tony-winning play helped to launch the careers of Dominic Cooper, James Corden, Russell Tovey, Samuel Barnett, and of course Dhawan. He originated the role of bright high school student Akthar at London's National Theatre, then played him again on Broadway and in the 2006 film adaptation.

2. An Adventure in Space and Time (2013)
Seven years before he first appeared in Doctor Who, Dhawan featured in Mark Gatiss' brilliant TV movie about the creation of the iconic sci-fi show. He plays Waris Hussein, the talented young director who called the shots on the show's first-ever serial, 1963's "An Unearthly Child."

3. Line of Duty (2014)
The BBC's hugely popular crime drama series (available to binge on AMC+) is all about "bent coppers" – officers who are in cahoots with the criminal underworld. Khawan appears in the second season as DS Manish Prasad, a colleague of Keeley Hawes' DI Lindsey Denton, who like her is suspected of being corrupt.

4. The Boy with the Topknot (2017)
Dhawan takes the lead in this BBC TV movie, an adaptation of Sathnam Sanghera's affecting memoir. He plays Sanghera, a young Sikh man growing up in Wolverhampton, England, who struggles to tell his family he's dating a non-Sikh woman (Joanna Vanderham). It's evocative stuff that offers a sensitive exploration of mental illness. 

5. Iron Fist (2017-2018)
Dhawan appears in the first season of this Marvel superhero show, but takes a more prominent role in the second. He gets to show off his action chops as Davos, an accomplished martial artist who is jealous of Finn Jones' title character because of the immense mystical powers he possesses. It's definitely a fun role for him.

6. The Great (2020-2021)
Dhawan has a key supporting role in the first two seasons of The Great, Hulu's raucous comedy-drama about the rise of Catherine the Great (Elle Fanning). He plays Orlo, a seemingly quiet and conscientious advisor who is getting to grips with the fact he's attracted to both men and women. It's a very sensitive performance from Dhawan.

7. Doctor Who (2020-2022)
In 2020's two-parter "Spyfall," Dhawan is introduced as a former MI6 agent who goes by the name of "O." However, Jodie Whittaker's Doctor soon learns that he is in fact her dastardly old foe, The Master. Expect him to cause even more trouble for The Timelord in this Sunday's special, "The Power of the Doctor."

Do you have a favorite Sacha Dhawan performance to date?