You have churchill, cromwell,challanger,centurion,chieftan,conquer and so on if anyone knows let me know cheers

There is also the Matilda :-)

Matilda, Valentine, Archer, Bishop also start with C :-) :-) Joke
Then you have some imported tanks, like Grant, Achilles, etc...

bye

Well, like everything in the British military in WWII, the answer is kind of complicated. I'll try to simplify it ... an impossible task.

Back in the 1930s, the British designated tanks as either Infantry Tanks or Cruiser Tanks. There were also some light tanks, i.e., Harry Hopkins, Vickers, etc.
Cruiser tanks started out with just different "Marks," but all those numbers and letters must have soon proved confusing, so Cruiser tanks ended up with names that started with "C" -- Covenanter, Crusader, Cavalier, Centaur, Cromwell, Challenger, Comet, Centurion.

It all went out the window with the Churchill. The Churchill was actually an Infantry Tank, like the Matilda, Valentine and Black Prince. Self-propelled guns had names all over the place: Archer, Bishop, Avenger ... then throw in all the American-built vehicles that were nicknamed after Civil War generals: Sherman, Lee, Grant, Stuart. The American M7 "Priest" prompted other SP guns to have clerical names: i.e., Sexton and Bishop.

bob is 100% correct,

C for cruiser was the original idea.

like bob says, the process of naming british military kit is confusing, some have names, some is their role abbreviated(Combat Engineering Tractor for example) and some just their FV number.

also bear in mind the names associated with US tanks, (sherman, grant etc) were actually first given to the vehicles by the british!

cheers

joe