Inspector Jim Cole and his team were at Peckham police station about to finish their shift on Saturday night when a call came in about pedestrians who had been hit by a van.
“Immediately, I thought it would be terrorist-related,” the 41-year-old said.
“We ran down to the yard and started getting the team back in the vans. it was like something out of a movie with police officers running everywhere. Everybody was jumping into cars, getting cars going.”
Mr Cole found wounded lying on the ground when he arrived at Borough Market minutes later.
“The people I saw had cuts and what I assumed to be stab injuries,” he said.
“There was somebody on the pavement, there was somebody else who was walking wounded.”
He heard gunshots and loud bangs soon after and had no idea if it was coming from the attackers or his fellow officers.
“From updates on the radio, we were aware that people had got out the van and were attacking people in the market,” he added.
“But we didn’t know if they were armed, how many there were or what the situation was.
“I heard a number of shots started ringing out and a lot of shooting going on.
“At that point, I didn’t know if the shots were us or potentially the attackers.
“Information came over the radio that they were wearing suicide vests.”
He and his team managed to get around 200 people to the safety of a pub cellar.
“We had the situation of people coming running out of the market, they were in a state of panic - lots of screaming,” Mr Cole said.
“So I literally just grabbed hold of as many as we could and directed them into the basement of the bar. I felt that was as reasonably safe a place as we had at the moment, rather than roaming the streets.”
He said he could hear his colleagues over the radio “in quite a state of distress” as they desperately called for ambulances.
“On the radio, I could hear officers up at London Bridge and outside the Mudlark who were doing CPR and they were calling for ambulances urgently,” he said.
“I would described it as pandemonium really.
“I went down into the basement - there was probably 200 frightened people there, all waiting to find out what happened.
“I felt I needed to say something to try to reassure them and let them know that we would be getting them out of there and they were safe.
“I told them that we had armed officers outside, everyone was safe and there was a nice big round of applause and cheering - that was really good and that felt good.”
The married father-of-three said the incident was the worst he has seen in 18 years as a policeman.
“I’ve dealt with things over the years - people stabbed or murdered and death - but it was the sheer scale of it all,” he added.
“I think I just went into autopilot, just kicked in. I’ve been a police officer for quite a few years, so all those sort of skills kick in and you just get on with it.”
He paid tribute to his colleagues, including Charlie Guenigault, an off-duty officer who was stabbed as he tackled the terrorists with his bare hands.
He said: “He was injured as he tried to take on people and in the aid of the BTP officer - it was phenomenal bravery really.
“Guys and girls on the response team doing CPR. A lot have been badly affected by it, really upset. Incredible bravery.
“Some of them were confronted by these guys and just got on with it. Hats off to them really.”
Mr Cole said that messages of support from the public “have been fantastic” and said the response from the London community “has been absolutely phenomenal”.
“We have all been expecting things to happen after what happened in Manchester and what happened in Westminster. It almost felt inevitable that something was going to happen,” he added.
“And you just have to get on with it really, get on with your job.
“It’s shown the best side of the Met really because in recent years, the job has felt quite tired and people have felt like they’re under strain and to see the response initially when the call came out with everybody rushing to get out and then the response of people pulling together and doing their bit is fantastic to see and makes you proud really.
“I think the way things are at the moment, we’re all on tenterhooks thinking that it could happen again.
“You just have to get on with it, go about daily life - if you start living your life fearful of walking out the front door, then you would never do anything really.”