Comet

The Comet was the last British tank design to see combat in WWII. It was essentially a bigger Cromwell with more armor protection and a much better gun. The 77mm was actually the same 76mm bore as on the 17lbr however it recieved the 77mm designation to keep it from getting mixed up. Essentially it was a 75mm that designers decided if it was bored out it could share the 17lbr ammunition but  the chamber wasn't thick enough to use the 17lbr charge. Also the barrel was a little shorter but they played with the powder to restore some of the muzzle velocity however it still wasn't quite as capable as the 17lbr. It was however miles ahead of the 6lbr and 75mm that was standard on earlier tanks.

In Game Edit
This is the tier VII British tank. It is the fastest tank in it's tier though has the least firepower but highest fire rate and is tied for lowest health. It is a very deadly tank on the battlefield, being able to go head to head against any foe. Its mobility is the biggest advantage against other tanks in its tier. It is best to remain behind the front lines as a support tank and only expose the turret when firing as it's a difficult target to hit. If you target the weak spots it can even do quite a bit of damage to the front of a Tiger II. In a close range fight with tanks in its own tier its higher mobility gives it a major advantage in a circling dogfight. Currently this faces experimental tanks which are much more powerful but slower. Your gun can still damage them with shots to the side or rear and dogfighting works pretty well thanks to those tanks slower turrets and turn rate.