The former president of Ukraine has applauded the growing round of expulsions of Russian diplomats following the nerve agent attack in Salisbury, saying "I have no doubt" Moscow was behind the attack and that military action against Russia should not be ruled out.
Viktor Yushchenko was himself poisoned in 2004. He and his family believe the assassination attempt was ordered by Moscow when he attempted to steer Ukraine to closer integration with Europe.
Speaking to Sky News, accompanied by his American-born wife Katarina, Mr Yushchenko warned that the new-found solidarity between European states and the US was not enough on its own.
"I have no doubt (that Russia carried out the attack). I want western society - western governments and European governments in particular - to have no doubt too," he told Sky News in his Kiev office.
"I totally agree with the British position. I am glad that it has received international support and solidarity. I think politically it is a very important position that is being developed with a united Europe and the United States. But I don't want it to end there with this single step, which we use to confront the modern imperial Russian policy."
Mr Yushchenko is critical of western policies towards Russia over the past decades.
He insists that every Russian attempt to interfere in the working of other countries should be addressed immediately, even suggesting that military involvement should not be ruled out.
Expelling diplomats is not enough, he said.
"If we are talking about Russian policy for the last decade or 15 years, it is dangerous," he explains.
"Of course we should talk about the diplomatic component, but we should talk about the military component, we should talk about the safety component, economic, financial, humanitarian, sanctions. All these components are a mosaic which contains all these components which makes one strategy focused on changing Russian policy," he said.
"Of course we can talk of a defensive military component - when every Russian provocation is answered. Answering is not aggressive. We are not talking about conquering. We are talking about a normal reaction to the aggressive action of Russia on Ukrainian territory today."
Katarina Yushchenko said that when she heard of the attack on the Skripals, everything came flooding back.
"Of course it did. My husband has been through it, many other people have been through it," she said.
"What we are seeing is the hybrid war tactics that Russia has been using in Britain, Europe and the U.S. - they are exactly what was done in Ukraine many years ago.
"We are talking about poisoning. We are talking about fake news. We are talking about the financing of radical parties. We are seeing the same thing. It was a frightening repeat of what we saw happening in our country," she said.
Mr Yushchenko led the so-called "Orange Revolution" - a series of protests and political events that took place in Ukraine from late November 2004 to January 2005.
The poison used to attack him was dioxin, a primary component in the defoliating chemical known as Agent Orange.
Mrs Yushchenko believes it wasn't a coincidence.
"Our doctor in Switzerland thought that it was ironic. Russia often uses symbolism, uses key dates, they often use these types of things to send messages, so yes, I think it might have played a role. There is no doubt it was made only (in Russia) and everyone involved with it ran away and is now hiding in Moscow," she added.
The former president says that the only way to control President Putin is a mixture of solidarity economics.
Reduce the use of his natural resources and the economy of Russia will fail, he says, adding that sticking together is the key.
By Stuart Ramsay, Sky News