A top Porton Down scientist says his “blood ran cold” when he learned the deadly nerve agent novichok had been used on British soil.
Professor Tim Atkins was on call on March 4, 2018 when police contacted him to say they were dealing with a chemical weapon incident.
Traces of the Russian-made nerve agent were found in Salisbury, Wilts, after Russian former double agent Sergei Skripal, then 66, and daughter Yulia, 33, were spotted slumped on a park bench.
Both survived and are now under police protection.
Exposure left Dawn Sturgess, 44, dead and her partner Charlie Rowley, and Wiltshire Police’s Det Sgt Nick Bailey seriously ill.
He has since retired from the force after 18 years of service.
Speaking ahead of the third anniversary of the attack on Thursday, Prof Atkins said: “My blood really went cold.
“While I suspected a chemical had been involved – and clearly a toxic one – I don’t think I ever predicted that it would be
something so hazardous.
“My mind turned to how am I going to explain to police what’s being used and what the likely consequences of such a hazardous material being released in a city are likely to be?”
A senior scientific adviser to the emergency services, Prof Atkins works at the Defence Science and Technology Laboratory, based at Porton Down, Wilts.
He had enjoyed the afternoon making snowmen with his children before news of the chemical attack broke.
Scientists then spent the next few days working to identify the substance.
Prof Atkins was at a police station when he learned that Novichok had been used.
He added: “The scale of the clean-up was enormous.”
Revealing he experienced a “real mixture of emotions” while leading the response to the attack, Prof Atkins said his work on Novichok, for which he was awarded an OBE, had taken a toll and that he is a “slightly different person”.
Tracy Daszkiewicz, 47, was appointed public health director of Wiltshire council just a few months before the crisis.
The mum-of-four said that she was left devastated by the death of Dawn, who inadvertently sprayed herself with Novichok contained in a discarded perfume bottle.
She said: “Losing Dawn was devastating. I remember getting the phone call and us regrouping... I can’t even describe it, just disbelief, and that whole realisation that you’re almost starting again.
“Major incidents are usually denoted by mass casualties, mass impact and, in worst-case scenarios, mass fatalities.
“This incident did teach me that one is too high a number.
“Everybody’s name matters, the fact we’ve only got one name, that name is as important as any other.”
Two Russian nationals have been accused of travelling to the UK to try to murder Mr Skripal.
Suspects Alexander Petrov and Ruslan Boshirov were seen on CCTV in Salisbury the day before the attack.
It is claimed they were officers from the Russian intelligence services, known as the GRU.
Moscow has repeatedly denied any involvement, with President Vladimir Putin once claiming the two suspects were civilians.