Heavy tank
The Char 2C was one of the largest tanks ever produced. At the start of World War II, France and the Soviet Union were the only countries to have inventories of heavy tanks, such as the Char B1, T-35, and KV-1. The Matilda II was designed under the British infantry tank concept which is similar to the heavy tank having thick armor and weighing more than their other tanks. It’s usually separate because they have less firepower with their cruiser tanks (comparable to mediums) at the time having the same main armament but more machine guns. Later war examples were the German Tiger I and II, as well as the Soviet IS series. Note that "heavy" versus "medium" is more a question of tactical roles than weight; the Panther, for example, was a "medium" tank that outweighed most Allied "heavy" tanks.
British heavy tanks of World War I
A number of tanks survive, although several are just shells that have had all internal components removed. The largest collection is at The Tank Museum at Bovington in the United Kingdom, which holds eight tanks. Two of these are maintained in running condition, the Mark IV Male, "Excellent" and Mark V Male number "9199". "Excellent" last ran in the 1980s and "9199" in the 2000s. The Bovington museum does not intend to run them again, due to the wear and tear that would be inflicted on the now-fragile, historic vehicles. Instead, the museum acquired a replica Mark IV tank (constructed for the film "War Horse"), which is used for public demonstrations.