The FV4201 Chieftain was the main battle tank of the United Kingdom during the 1960s, 1970s and 1980s. This is the one on display at the Tank Museum at Bovington.
A development of the Centurion, the Chieftain introduced the supine (reclining) driver position to British design allowing a heavily sloped hull with reduced height. A new powerpack and improved transmission gave it higher speed than the Centurion despite being heavier due to major upgrades to armour protection and the armament.
Still in service in the Middle East, the British Army stopped using it in 1995.
I did consider buying some for Team Yankee, but was put off by apparent issues with the smoke dischargers on the side of the turret. Certainly for a 1970s version of Team Yankee you couldn’t use the new Challenger, and would need to use the Chieftain.
There was also one on display at Duxford.