We had just come out of a very busy weekend. A major incident had been declared because of snow. I was the on-call chief officer and at 8pm on Sunday 4 March I got a call from a superintendent who said: “Boss, you’d better sit down for this one.” Two people had been taken gravely ill in a public place. We were keeping an open mind, but with Mr Skripal’s background, there was a sense that all wasn’t right. There were a number of hypotheses, from food poisoning to drug overdose to something more sinister.

Our number one priority is to save life. We were working with the hospital but were also in contact with the Defence Chemical Biological Radiological and Nuclear Centre, just outside Salisbury, for advice on scenes, protective equipment, signs and symptoms, and outcomes for Sergei and Yulia Skripal. I spoke to the counter-terrorism network, which was growing massively as the intelligence picture emerged. [Last month, police released more video footage of the suspects.]

Facebook Twitter Pinterest Yulia and Sergei Skripal. Photograph: Rex/Shutterstock

By Tuesday, we were aware a chemical was involved. The chief scientist at the Defence Science and Technology Laboratory at Porton Down (known only as Professor Tim, for security reasons) told us there was every indication this was a nerve agent – the first time one had been used on mainland Europe since the second world war. There was a sense of disbelief.

We ended up with nine cordons around Wiltshire, with 90 officers in total protecting them. We only have 950 – we’re one of the UK’s smallest forces – so were assisted by 40 forces providing 700-800 officers. The investigation was led by counter-terrorism police. My role, as chair of the strategic coordinating group, was consequence management – local issues, logistics, public health, public confidence, talking to scientists. We spent eight weeks in response mode before starting to return to normal.

On 3 July I was watching the England match [against Colombia in the World Cup] when I got a call from Professor Tim. I was aware there had been an incident in Amesbury. The lead theory was that Dawn Sturgess and Charlie Rowley had been exposed to a bad batch of drugs. Professor Tim said: “Paul, I’m 75% certain this is novichok again.” I declared a second major incident.

Facebook Twitter Pinterest Video footage of the suspects. Photograph: Reuters

I was shocked. You start to challenge yourself: have we missed something? Had we exposed people to risk, told them things were clean when they were not? Where’s the novichok been if it’s the same batch? Or have we been attacked for a second time?

We had to give out the difficult message that we couldn’t guarantee there wasn’t more of this stuff out there. We didn’t think there was, but we couldn’t rule it out. Dawn’s death was tragic. Our hearts go out to her family and to Charlie.

The resilience of the communities in Salisbury and Amesbury, and the way the public came together, is humbling. We’re hugely proud of how a small force coped in an international incident. DS Nick Bailey [one of the first officers to enter the Skripals’ home] suffered novichok poisoning and continues to recover, physically and mentally. Nick put himself on the line as all police do. There was a luck factor here. To this day, I’m still amazed more people who responded didn’t become poorly.

As told to Steven Morris

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