On the Coachbuild website it says it's "probably" a T87.
The T57 was only made until 1947 and since the puzzle car is from 1949, when the T87 was being made, I didn't question it.
But it does look far more like a front-engined car than a rear-engined one, so you're probably right!
Here's a better photo than the one used for the puzzle: