It is an evolution of the Churchill, called the Black Prince, it is much larger to allow for a 17 pdr gun but it has the same engine as the Churchill.
I am aware of the existence of the Black Prince, but I wasn't sure if it was supposed to be representing either it or a Churchill, since the Black Prince was supposed to be massive, even when compared to the Churchill. Could be a trick of perspective, but it seemed to be too narrow to be a Black Prince. Now that I have taken a closer look at it, I'd say that it is in fact, the Black Prince, based on the bogie design.
It would probably be funny to see a Pz IV fail to penetrate a Black Prince frontally or a Panther surprised to see that a lumpy Churchill actually punched through them at 1km... and then there's the Tortoise with its literal "I can fight you at any range and you can't punch through my frontal armor" air.