"We've got the highest levels of controls of security around the work that we do here," Gary Aitkenhead told me.
"We would not be allowed to operate if we had lack of control that could result in anything leaving the four walls of our facility here.
"There's no way that agent would have left. We have complete confidence that nothing could have come from here out into the wider world."
The above comment from the head of the Porton Down laboratory (10 miles from the Sailsbury incident) sounds like an acknowledgement that they stock the Russian nerve agent used in the attack.
http://www.bbc.co.uk/news/uk-43520534#