It's my understanding that king Alfred is such an old variety that the true form is actually quite rare if not extinct. Growers use the name and sell several generic yellows under the label, so it's even possible you'll get Dutch master when you buy something labeled king Alfred.

so I suppose I'm saying get the Dutch master. That should be a healthy, vigorous variety and exactly what you order.

I wonder why your daffs have not filled in along the closer end of the wall. It's likely that even the replacements will fade away unless you find a reason they're not as happy there.