Taskmaster

I've never watched Taskmaster, although I have seen trailers. Wikipedia obviously has watched it, however; and it says that the Taskmaster is Greg Davies, "issuing simple comedic and bizarre tasks to five regular contestants."

According to Wikipedia, Alex Horne created the show for the Edinburgh Fringe, in 2010, and "[acts] as Davies's assistant and as umpire during the challenges."

Sounds to me as if the best answer to this question is Greg Davies.

Wikipedia also says that Taskmaster "was acquired by Channel 4" in 2019.