This time we have the completed HD model and textures.
The Turtle name is a WG joke on the Tortoise. The vehicle was the result of a the School of Tank Technology project in 1946, unfortunately the concept was already obsolete. Very little documentation survives save for a single image with the layout and dimensions. According to Ed Francis (historian at Bovington tank museum, responsible for providing a lot of interesting information about British tanks) WG did a good job during the reconstruction of the vehicle, so we can assume that it is faithful to the concept.
Source Wot Express and DoM1N.