Complex sentence: Rudi then worked at the National Theatre on the original London stage production of "The History Boys", understudying the role of Dakin, ably took over as Crowther in London when stepping in for and later making his debut on Broadway in the role of Crowther.
Split into simpler sentences: Rudi then worked at the National Theatre on the original London stage production of "The History Boys", understudying the role of Dakin. Rudi later making his debut on Broadway in the role of Crowther.