Why Britain retained rifled tank guns

Why did Britain take so long to change the guns fitted to its main battle tanks?

It preferred the perceived accuracy of rifled guns, until the cost of the separate approach and ammunition supply became harder to sustain.

Britain's retention of rifled main guns is explained through a preference for treating its tanks as accurate long-range shooters. That preference justified following a different gun path for a time. Eventually the cost of maintaining a separate approach became harder to accept. The end of domestic ammunition production is also mentioned as a constraint.