What we were to soon learn was that those two people, former Russian spy Sergei Skripal and his daughter Yulia, had been contaminated with military grade nerve agent Novichok which had been applied the front door of their home in a quiet street a short drive away from the city centre.
Both were rushed to Salisbury District Hospital where Sergei remained for almost six months and Yulia for just over a month. Days after they were admitted, one of our officers, Detective Sgt Nick Bailey - who had been part of the initial response to the incident, fell critically ill and was also taken to the hospital. Thankfully, he too was discharged from hospital a few weeks later.
Over the next few months, close to 2,000 officers, staff and volunteers from across the country assisted us and the Counter Terrorism Command with the investigation and the guarding of the 12 cordoned scenes put up in Salisbury and Amesbury.
Complex, demanding and high profile
Chief Constable Kier Pritchard, whose first day in the job also fell on March 5 said: "This case is without doubt the most complex, demanding and high profile we've ever had in Wiltshire.
"Every day there was a new development or another twist which would not only test the resilience of my officers and staff but the communities we serve in the south of the county.
"The response we had, and continue to have, from the public is astonishing. To this day, there are still people in the city who take the time to come up to my officers and thank them for their dedication and diligence over 2018.
"I will be honest, this investigation and the subsequent, tragic death of Dawn Sturgess in Amesbury a few months later, tested us to our limits.
"Of course the thoughts of everyone in Wiltshire Police continue to go out to all those who have been affected in some way through the significance of these incidents
"This first anniversary gives us the opportunity to briefly pause and reflect on the enormity of the task we faced and the outstanding work each and every one of my officers, staff and volunteers did and continue to do whether directly involved in the incidents or maintaining the vital business of policing the rest of our county.
"2018 was a year of unprecedented demand and pressure but more importantly, it was the year of extraordinary togetherness - we rallied around our communities and they rallied around us."
2 - suspects identified as Alexander Petrov and Ruslan Boshirov (believed to be aliases)
5 - people confirmed to have been contamined by Novichok
7 - number of charges against the two men responsible
12 - number of scenes
400 - number of exhibits seized by Counter Terrorism police
530 - number of Wiltshire Police officers involved
1,200 - number of mutual aid police officers drafted in to support us
£12m (approx) - the estimated cost of the operations
Wiltshire and Swindon Police and Crime Commissioner, Angus Macpherson said: "It's fair to say that the past year has been a difficult one for those in South Wiltshire, and it's important that recovery efforts continue to support those in Salisbury and Amesbury.
"It was incredibly important to me that we were not left to shoulder the financial burden of what was an international incident, and I'm pleased to have been able to keep the Home Office up-to-date on the operational costs and for this to have now been reimbursed in full.
"The two incidents saw a huge demand placed on all emergency services and our partner agencies. Wiltshire Police faced a period of extraordinary pressure, which saw 1,200 officers from every other police force across the country come and support us.
"So many people were affected by what happened on March 4th 2018 and the subsequent events that followed and my thoughts continue to be with them, in particular the family and friends of Dawn Sturgess.
"The community spirit and support has been unfaltering in the past 12 months. Last year we truly saw the very worst but the very best of humankind."
|What is Novichok?|
A military grade chemical weapon developed in the Soviet Union in the 1970s & 1980s
It can take many forms - liquid, gel or powder
Is extremely difficult to detect and is persistent