“...if you can’t believe British intelligence, whom can you believe?”
Well, it all seems perfectly logical. According to the official narrative, the Skripals came in contact with the Novichok by touching the door handle of their house. (Note that Novichok is supposed to be ten times more deadly than VX.). After touching the door handle, they went to feed the ducks, then went for a drink, then went for lunch at Zizzi’s, at which they consumed a rich sea food dish of clams, mussels, king prawns, etc. all washed down with white wine. Then, five hours after the door handle contact, they went for their famous walk in the park.
And after falling sick from contact with the deadliest nerve agent known to man, they have made a full recovery.
So what’s not to believe?
And after falling sick from contact with the deadliest nerve agent known to man, they have made a full recovery.
It's not the deadliest nerve agent known to man.
And you don't want it to work instantly, that would make it difficult for the person who planted it to make their escape.
An example would be the Ricin attacks made by Soviet bloc agents during the Cold War.