After his role in the West End theatre production of Milked, Cartmell became the voice of the titular character in British Where's Waldo television series.
[6] Shortly after, Cartmell played the role of the Mind in Borderline Electra, written by Stevie Helps, in Manchester at the Lowry.
[2] On 18 December 2020, it was announced he would be voicing Gilber in the Netflix original series Go, Dog.
[8][9] In November 2021, he had a guest star role in the BBC medical soap opera Doctors as Jack Turner.
[10] On 6 September 2023, Cartmell reappeared in Doctors, this time in the role of Henry Povall.