As cuch said, the likeliest explanation might be a leak.
Another explanation might be that this was a random attack by the Russians to throw us off the scent. Like the old theory that if you want to kill someone, you kill a bunch of random people first so the police are looking for a serial killer and won't suspect you.
The couple have been named as Charlie Rowley and Dawn Sturgess by an Amesbury resident who claims to be their best friend.
Sam Hobson, 29, told reporters that he saw Ms Sturgess being taken out of Amesbury Baptist Church at 11am on Saturday.
Mr Rowley slumped into a "zombie-like state" several hours later at his home in Muggleton Road, he claimed.
"We were preparing clothes to take to Dawn in hospital," Mr Hobson told South West News Service. "He felt ill and went for a shower. Then his eyes went bloodshot and like two pin pricks, he began garbling incoherently and I could tell he was hallucinating.
"He was making weird noises and acting like a zombie. He slumped against the wall.
"Everybody is saying it's drugs related but Dawn doesn't take drugs. This doesn't make any sense - I can't see why they'd be targeted, it's completely random."
A source told The Independent there are no obvious connections between this case and the Skripals.
The couple are British and have no known link to espionage. Could they have been affected by residues of the novichok-based agents used on the Skripals? It is thought that should have dissipated by now.
the story ISM linked seemed to think that it was relevant that this couple were found "near" to where the Skripals were found. Elsewhere in that article, it said the two incidents were 10 miles apart.
If people were to be "affected by residues of the novichok-based agents used on the Skripals," I would have thought it would have happened much sooner and to more people.
The theory that was settled on for the Skripals after what, half a dozen earlier theories (gas through the car vents and so on) was that poison was placed on the door handles of their house.