Not only that, unless Porton Down already has some samples of novichok, how can they assess what "grade" the Salisbury stuff is? What are they comparing it with? How do they know anything about novichok, its grade, its purity, etc., unless they have some? And is there such stuff as sub-military-grade novichok???

Suppose I lived on a desert island and had never seen a Brussels sprout. You arrive on the island and give me a sprout to taste. I say wow, what a superb sprout! I've never seen one (at this you raise an eyebrow...) but I can confirm that the one I've just eaten is an absolutely first-rate example of sprouthood! Top grade! So pure! Restaurant quality!

Yeah, right, you'd say...!