Commuter Neil Perkins, 22, a recruitment consultant from Maidstone, was sitting close to Miss Banks before she went into labour. He said his "jaw dropped" when he realised she had given birth.
We got to West Malling and the train stopped. The driver asked for anyone who was a doctor or nurse to make themselves known, and I thought someone had been taken ill.
I jumped off the train and I saw everyone running to the carriage behind us. I called my mate to see if he could pick me up and then the lady started screaming. They were big screams.
I was a bit worried for her, but the driver ran up and said not to worry, someone had just gone into labour.
The lady was screaming quite loudly, and me and a South African lady were saying that the ambulance needs to hurry up.
Then, minutes later, I heard a lady shout out 'It's a girl!' I was just in shock.
As I walked down I could see the mum wrapping the baby in a jumper or something and giving it a cuddle.
It was madness, then the ambulance turned up. It was a really exciting moment. I have never witnessed anything like it.
I hope the girl gets free train tickets for life.
More top news
A miniature Shetland pony has surprised its owner after unexpectedly giving birth to tiny 17-inch tall foal.
A six-year-old girl was bitten on the legs by a police dog while officers were chasing a suspect.
Taiwan has taken a new approach to covering the Labour leadership contest.