Skripal poisoning is a well-planned operation by the British intelligence. UK knew that some Russians are coming to Salisbury for “negotiations” and used this opportunity to accuse Moscow of poisoning.
UK police and intelligence investigations have produced hard evidence which is sufficient to charge two Russian nationals for the attack on the Skripals. These two individuals have been established as officers of the Russian Military Intelligence, GRU. More UK public documents/statements on the case here and here.
The EU Member States support the UK findings, and decided unanimously to introduce sanctions against the GRU officers responsible and their commanding officers.