The Cruiser Mk II (A10) was developed as a heavier version of the Vickers A9, with armour of up to an inch thick, double that of the A9. Unfortunately as the engine was still the same, this slowed the tank down to 16mph, but with the thicker armour it didn't need to be quite so fast... so all was good.
Originally it was designed as an infantry support tank, but the speed of development meant that it was shelved, later revived as a heavy cruiser instead. After 175 were produced, the slow speed and relatively thin armour compared to other tanks on the battlefield at the same time led to it being mothballed.
A number saw service with the BEF in France, but performance was reported as very poor. On the other hand, some also saw service in the defense of Tobruk where it's speed and performance suited the environment. The remains were taken to Greece, where they performed well, but over 90% were lost due to malfunction, rather than combat.
The track guard seems to be made of perishable rubber as you can see here from the warping/cracked state.