The
Tank, Cruiser, Challenger (A30) was a British tank of
World War II. It mounted the 17 Pounder gun on a chassis
derived from the Cromwell tank to add heavier anti-tank
firepower to the cruiser tank units.
The design compromises made in fitting the large gun onto
the
Cromwell chassis resulted in a tank with a powerful
weapon, but with
less armour. The extemporised Sherman
Firefly
conversion of the US-supplied Sherman to take the
17 pounder was easier
to produce and, combined with delays
in production, meant that only 200
Challengers were built.
However, it was able to keep up with the fast
Cromwell tank
and was used alongside them.
http://en.wikipedia.org/wiki/Cruiser_Mk_VIII_Challenger