Unstated, but the implication is the security services and quite naturally we are unlikely to be given details for reasons of operational integrity.
There is an undoubted politically expedient motive to the UK response to the attack and I recall a source at PD expressing disquiet at the high-level political pressure that was put upon them to confirm it was a poison of Russian origin.
Edit:
Have a read of this,:
UK urged to counter 'disinformation' from Russia over novichok
https://www.theguardian.com/uk-news/2018/apr/04/uk-urged-to-counter-disinformation-from-russia-over-novichok?CMP=Share_AndroidApp_Copy_to_clipboard
There is an undoubted politically expedient motive to the UK response to the attack and I recall a source at PD expressing disquiet at the high-level political pressure that was put upon them to confirm it was a poison of Russian origin.
Edit:
Have a read of this,:
UK urged to counter 'disinformation' from Russia over novichok
https://www.theguardian.com/uk-news/2018/apr/04/uk-urged-to-counter-disinformation-from-russia-over-novichok?CMP=Share_AndroidApp_Copy_to_clipboard