Why do they speak 'perfect' Spanish in Valladolid?

Europe

It’s a long-held belief in Spain that the best and purest Spanish is spoken in the northern city of Valladolid. How did this claim come about and is there any truth to it?

It’s a long-held belief in Spain that the best and purest Spanish is spoken in the northern city of Valladolid. How did this claim come about and is there any truth to it?