The FV4201 Chieftain was the main battle tank (MBT) of the United Kingdom from the 1960s into 1990s. When introduced, it was among the most heavily armed MBTs of the era, mounting a 120 mm Royal Ordnance L11 gun, the equal of the much larger specialist heavy tanks then in service. It also was among the most heavily armoured, with up to 195 mm (7.7 in) that was highly sloped to offer 388 mm (15.3 in) thickness along the line of sight.

Iconic, mostly for the huge amounts of blue smoke that pour out the back of these, if they're running, which a lot of the time they weren't!

prompt: a <chftntank tank> does <things, including breaking down, emitting blue smoke, or waiting for desperately needed technical changes>