The tug looks like a Douglas / Sentinal Tugmaster, built by Sentinel of Shrewsbury.
We used them back in the 70s to tow Britannias at Brize Norton. Some had cabs, some not. There is one currently residing at Kemble.
Regards,
Paul.
Now having said that I have looked at a picture of a Sentinel Tugmaster, and in the picture below, the bottom half is Sentinel, and the top half looks like Leyland Martian? Curiouser and curiouser.