Travel with Angela Lansbury: How to report an incident on a train?

Long ago I experienced an incident in Harrow, NW London. England, the police told me that if they had a photo of the trouble-maker, it was usually easy to track them down.

Photo Identity
Police Photos
I asked my family about this. Nowadays with social media, it is relatively easy to put up a photo and get the person identified. Back then a simpler method was used. Suppose, for example, a lad threw a bottle, or tried to break into a car, or assaulted somebody in a pub? First, the police have a book of photos of regular offenders they can show you.

School Photos
They can take a photo of the offender around the half a dozen local schools and ask the head teacher, is this person at your school? If the person is a teenager or in their twenties, it might still be possible to identify them from an old end-of-year school photo.

Now, let's move to 21st century Singapore, where every station has video cameras.

After an incident, I was aware that I could not identify which train I was on, because trains run every three minutes and I reckoned it had taken me longer then three minutes to walk along the platform, go up the escalator, and walk to the ticket office and get attention and tell my story. At the end, I was asked, 'When did this happen?'

I said, "I am not sure. I suppose if it ever happens again, I should look at my watch and note the time the incident happens and the time I got off the train."

The station staff member told me, "Your watch may not be sufficiently accurate. What we can do is track you leaving the train and going up the escalator and through the station to work out the time of the train, and then alert staff at the next station or later stations.
(More later.)

Trains line up with the platform glass doors. If you can identify the door on the platform, where you exit, we know where you were on the train.

Reporting People In Incidents
To identify an alleged culprit, victim, or witness, violent person, or sick person, staff may want to know about the person. Try to describe:
Sex
Race
Language spoken
Age
Hair: bald, thinning, thick, black, brown, blonde, red, white, straight, curly, ponytail, long, short, below or above ears, parting.
Clothing: colour, style, shoes, trousers, t-shirt, slogan on clothes, hat, gloves.
Accessories: mobile phone, shopping bag.
Action: (Molesting, photographing, shouting, swearing, threatening, lurching, collapsing, talking on phone, talking to themselves, singing, aggressive, dazed.
Position: sitting, standing by door, walking up and down train.
If you can take a photo without obviously doing so, it's easier for you to report accurately.