Human beings, who by and large are not inbred or even line bred, and at least in the UK are a mongrel mixture of breeds, die prematurely of heart attacks, strokes and cancers, many of which are hereditary; they suffer from epilepsy, SM, muscular dystrophy (hereditary), multiple sclerosis, immune diseases, haemophilia (hereditary), mental health problems, etc, etc. Yet most human beings are wonderful, and the human body generally does a great job. Our Cavaliers ARE wonderful - get two Cavalier owners together and they will start telling each other how wonderful their dogs are. And even when we have coped with MVD and SM, we still buy another one because, for us, there is no other breed quite like them.
If Belinda of Saxham, so far back, had MVD (though there are a lot of other heart diseases that dogs can die of), perhaps she inherited it from the King Charles Spaniels who were the forebears of Cavaliers, and it was not the fault of the early Cavalier breeders at all. Charlies, with their domed heads and flat faces, are just as much a 'designer' breed as Cavaliers, and they have their own disease problems - but not so obvious because there are far fewer of them. Blaming breeders about whom you know little and never met is rather like a human being blaming their cancer on a great-great-great-great grandfather who might have introduced the cancer gene into the family. We just don't know, and it's a waste of time trying to find a culprit. So please save your energy to attack the modern breeders who refuse to learn from the past - you do a great job there, Bet, for which we all admire you!
Kate, Oliver and Aled