You must have been living under a very big rock at the time....

You must have been living under a very big rock at the time. After Alexi recovered from being Novichoked he rang one of the thugs that did the poisoning. The bas***d thought he was speaking to one of his superiors and explained on tape exactly where the Novichok was placed on the seam on Alexi's underpants. You can't be more accurate than that, straight from the horses mouth.

I have no idea where you found the other two options, for starters Poo-Tin's thugs usually prefer Polonium for tea, not Novichok and the hotel water bottle? You probably pulled that out of where the sun doesn't shine.