A "very rare' nerve agent". That is what the UK's Interior Minister says was used to poison a former Russian spy and his daughter.
Sergei Skripal and his daughter Yulia were found unconscious on a park bench in the British city of Salisbury on Sunday. It follows several other mysterious deaths of Russians in the UK over the past few years.
Some had defected to Britain and had made allegations against President Vladimir Putin or his country's security services.
Those accusations often involved political assassinations, killings of civilians in bombings and running multi-million dollar corruption rackets.
So, what will be the implications of this latest attack? and what steps will Britain take to prevent such killings in the future?
Bill Brower - CEO and Co-Founder of Hermitage Capital.
Annie Machon - Former MI5 Intelligence Officer.
Samuel Greene - Director of the Russia Institute at King's College London.
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