Just out of curiosity, why do all Britsh tank designations start with letter C?
In my opinion, it also come from field experience. The full inventory name of the vehicle are quite long and confusing and simplify it in the field is a common practice. The main principle of using the “C” for Cruiser, or British equivalent to other medium tank, remain the same.
Say, the Tank, Infantry, Mark I - Matilda. Then the second Infantry tank is the Tank, Infantry, Mark II - Matilda II. The type, mark name then nickname, the nickname change when the mark change. Then in the Matilda II, you have Matilda II mk.2, mk.3, mk.4.
Tank, Infantry, Mk III, Valentine has eleven marks. Both of these tanks were designed very early phase of WW2.
So instead of calling it the type, like Cruiser mk or Infafntry mk, people used the nickname + the mark after the nickname on the field. So the starting “C” remained as an the type identification. Otherwise, it would be Cruiser mk x “X name” mk x with “X name” mk x does not share the anything in common with “X name” mk III, even though they are both listed as in reports Cruiser mk x. Look at the Tank, Cruiser, Mk VIII, Cromwell/Centaur, both bear the same Cruiser mark, both play the same role, but vastly different in maintenance between the two, let alone the different among their own marks.
The Infantry, or heavy tank equivalent, didn’t get a starting letter because by the time the reorganized the inventory name/number, the Infantry type were out of favor, with the last is the Tank Infantry mk IV Churchill.
Then we get to the era of MBT. Like all other nations, MBT started out as medium tanks. As such, the Centurion was developed as a cruiser tank. After the war, a new inventory system was put in place, this is the the FV (Fighting Vehicle). Under this system, all Tanks start with “C” because “Tank” became the sole type.