The FV4201 Chieftain was the main battle tank of the United Kingdom during the 1960s, 1970s and 1980s. It was the “most formidable main battle tank in the world” at the time of its introduction in 1966 with the most powerful main gun and most effective armour of any tank yet made.[not in citation given]. This was further improved while in service with Chobham armour upgrades.
Additional Information: en.wikipedia.org/wiki/Chieftain_tank