What I can't understand is that whoever did it waited so long. I believe Skripal came here after having been exchanged for British double agents in 2010.
And how did the perpetrators carry the nerve agent and smear it on the car door handle without dying immediately themselves? The personnel dealing with the crime scene are wearing extremely protective suits like astronauts. One would have noticed someone dressed like that lurking around the car surely?
It's similar to Litvinenko's killing using polonium. The people who did that would probably die too. The entire place was radioactive afterwards.
I think the nerve agent used was developed by the Russians, and unobtainable here.
Normally, one would want incontrovertible proof before enraging Putin et al. But to me there's no other credible explanation.
What worries me is that it's demonstrating just how few allies we have, and our own defence systems are woeful now. We're just a small nation with no teeth. It's a bit foolhardy to antagonise the Russians without huge provocation. Like poking a lion with a stick.