Why County-class cruisers used four twin turrets

Why did British County-class cruisers use four twin eight-inch turrets instead of three triple turrets?

Four mountings gave better redundancy: losing one cost a quarter of the battery instead of roughly a third, while four triples would not fit the treaty displacement.

The Royal Navy preferred four twin eight-inch turrets over three triples on the County class. Losing one of four mountings removed a quarter of the main battery, whereas losing one of three removed about a third. Four triple turrets would have offered both more guns and the same number of mountings, but the 10,000-ton treaty limit made that arrangement unrealistic. The design choice balanced firepower and redundancy within the displacement ceiling.