It was a summer evening, and I was on my way home from work on the London Underground. It was about 5.30pm when I changed from the Victoria to the Northern line at Stockwell. The platform was packed and very hot. I stood right at the far end, furthest from where the train would come into the station.

I could see the train lights reflecting off the wall opposite the platform before it arrived. Sometimes, if it’s really busy, the trains slow down as they come into the station, but this one was coming at a considerable speed. Suddenly, the woman standing beside me pushed away from the crowd and leapt, head first, into the space between the tracks.

When you travel regularly on the tube, you don’t think about the track or look into that abyss. But I was forced to confront the very real possibility that this woman would be killed. There was no time for analysis – something subconscious kicked in. I didn’t think about my life. I needed to help. As soon as she fell, I dropped my bag and jumped down after her.

I didn’t know whether the live rail had been turned off; I didn’t want to risk touching anything. The train was coming fast towards us. I tried to work out how far away it was and how long I might have to get her up and on to the platform. I wasn’t even looking at her, but she was out cold after hitting the ground, and difficult to lift.

The train came closer and people started to scream. Then a gentleman put his hand out and grabbed mine. He dragged me and I dragged her. By the time we scrabbled on to the platform, the train had stopped just a few feet away. Had he not helped me, or had we been five metres further up the platform, the woman and I would have been under the train.

Everyone crowded around us, asking if we were OK. I was still totally focused on the woman. She didn’t realise what had happened. After talking to her for a couple of minutes, trying to calm her down, she came to her senses. She was upset and disturbed – and certainly didn’t see me as a hero. Despite that, we had a long conversation about how she had come to be in this position.

The paramedics arrived and took over her care – she was disoriented and in shock. The man who helped me had melted away into the crowd, and I didn’t have a chance to say thank you. It turned out that CCTV cameras had captured everything, so the station staff had turned off the traction control on the train, effectively cutting its speed. I don’t know whether the driver even knew we were on the tracks.

After the initial shock had passed, the mood was quite strange. The people immediately around us were very concerned, but further down the platform, where no one had any idea about what had just happened, people were starting to get grumpy about the delay. It was life and death to three people, but just an irritation for hundreds of others.

We waited for an hour while the police, station staff and paramedics sorted everything out. Eventually, I was allowed to leave and the trains started running again. As I moved away from the situation, everything kicked in. I got on a train, sat down, alone, and thought: “Did that just happen?” I couldn’t believe how much danger I had put myself in, but also realised how great my own life was. You can’t make a phone call underground, so I couldn’t talk to anyone.

I work in the legal department of a brokerage and had had a really tough day; seeing the woman jump put things into perspective. I have always been encouraged to be kind, to watch out for others, to go the extra mile. As a Muslim, helping humanity is very much at the core of my faith.

When I got home, I told my mum. She was really upset, but after she had calmed down she hugged me and told me she was proud.

I have heard the woman I helped is doing well, and I am happy for her. Every time I hear a train, I think about what happened. I am now much more conscious of the people around me, and where I am standing on the platform. It was surreal and scary; but if it happened again I would do the same.

• As told to Camilla Palmer

• In the UK and Ireland, the Samaritans can be contacted on 116 123 or email jo@samaritans.org or jo@samaritans.ie. In the US, the National Suicide Prevention Lifeline is 1-800-273-8255. In Australia, the crisis support service Lifeline is 13 11 14. Other international helplines can be found at befrienders.org.

Do you have an experience to share? Email experience@theguardian.com.