The last iteration of the British heavy tank series was the Mk VII. It attempted to improve crew conditions, and have an ability to cross wider trenches, and in some ways did. However it's limitations and the end of the war closed this chapter in tank construction. It's design and production included input from the Americans.
Crew conditions were abominable in WW1 era tanks. The British heavy Mk series of tanks were the worst culprits, as the crew shared their quarters with the engine. Anyone who has worked on a pre-1920 type engine would understand how bad that could be, enclosed with an oil and fuel leaking monster that produced copious amounts of noxious fumes. In the Mk VII, the engine was at last enclosed in the rear behind a bulkhead, shielding all but the motorman from it's effects. This inevitably made the tank longer, which was seen as a feature that allowed it to cross wider trenches. This feature made turning the tank harder, and it was much tougher on the tracks, snapping them in the process. Different track designs were tried, and finally a track design that was barely adequate was settled on. Turning the tank, especially in wet weather and sloppy mud was never fully overcome.
To keep the weight down, the armor plate was skimped on, leaving the Mk VII with armor that wouldn't be acceptable by WW2. This left the machine still vulnerable to artillery fire, something the Germans had adequate amounts of. In the end, the prototype ran under it's own power on the day of the Armistice, and after that only a little over a hundred tanks were built. Production of any type of war material came to an end soon after, ensuring the demise of this version of the heavy tank. The Canadian ended up with American production of the machine, which amounted to most of them. The British had only built seven and that was it for them.
There are still a few examples around. There is one at the excellent Bovington tank museum, and a couple in American military museums, An American Mk VII with a converted Liberty aircraft engine is interred at Fort Meade's museum, while another is at the Aberdeen Proving Grounds at the Ordnance Museum, however this one is being relocated north of Baltimore at Ft. Lee.
This video shows the movie version of a Mk VII, from "Indiana Jones and the Last Crusade". It's built on an excavator chassis and built to look like a Mk VII, with a turret added. From philtydirtyanimal's channel.