Britain's foreign minister has vowed to respond ‘robustly’ to Sunday's attack on a former Russian spy living in the UK.
Sergei Skripal and his daughter Yulia are critically ill after being exposed to what police say is a nerve agent.
"If this does turn out to be in any way the result of hostile activity by another government, directed, led by another government then the people of this country can be absolutely sure that the UK will respond robustly", said Boris Johnson.
Annie Machon, a former British intelligence officer, has cautioned against jumping to conclusions about who must be responsible.
"I think this is a good first step. They've identified what it is. It will be a good lead to the further police investigation but I would still suggest that the the media and our politicians should not go stampeding towards you know - 'it has to be Russia. It's always Russia'. There are many, many other players."