The Salisbury poisoning could have been a farce prepared by London, with Sergei Skripal playing the lead role. But in the end, the British probably miscalculated the poison dosage, or actually decided to kill Skripal altogether.
No evidence given. This is a recurring pro-Kremlin disinformation narrative about the Salisbury poisoning. The disinformation message has been created as a series of inconsistencies, implying a British government conspiracy behind the Skripal case.
British police have presented a solid chain of evidence about the Skripal case, including pictures, that connects the two identified suspects to particular locations in the case. Parts of this material have been released to the public.
The claim that the UK allegedly staged the poisoning is an unfounded conspiracy theory.