Like many other people, I watched Adrian Pinsent’s video of coffee shop staff at Waterloo station last week refusing to let him buy food for a man with no home and an empty stomach. A member of staff claimed that it was company policy and the rules of the station. The employee was wrong, it turned out – but the incident brought back some vivid memories for me.

I recently spent several months in central London recording 30 homeless people as they chronicled their lives with great candour and humility. Much of what they talked about was their life, now, on the street. No front door key. Few possessions. Little dignity. I collected their stories and called the book Four Feet Under, because they live four feet under the rest of us.

He beat me down the right-hand side of my body and legs so hard that I was deeply bruised for 10 days

I recognised that tone of disbelief in Pinsent’s voice, as he found himself pleading to buy food for a hungry man. There was a kind of madness in the sketch. My own voice had had that same tone on the very first day of my travels among homeless people. I was on the Strand on a chilly October dawn and went into a McDonald’s to buy several coffees, as I’d seen a group of young men waking up on the pavement outside and thought they could use a hot drink. I ended up in a huge argument (I didn’t have Pinsent’s restraint) with the two security officers – complete with earpieces like the Men in Black – who would not let me make the purchase. “It only encourages them,” they told me. Encourages them to what? I was livid and within no time I too was barred from the premises.

That was the first of many examples I witnessed of the treatment homeless people receive on a daily basis. Why is this so? Perhaps we are now such a fractured and injured society that even the weak will attack the weaker, and people with much cannot endure the sight of those with nothing. Is it a twisted form of shame when we know the number of children who are homeless or in temporary accommodation has risen by nearly 40% in the last three years? The man Pinsent was trying to help would not have been shocked at all. He would have seen it and endured it many times before.

Adrian Pinsent’s video of Costa staff refusing to sell him food for a homeless man.

The hours of darkness are open season on homeless people. It is a common sport for drunk club-goers to urinate on them as they sleep. Aside from the fact that it’s disgusting, it has a further consequence: that person now has no usable bedding. No laughing matter in winter. Many – women included – are beaten and kicked until the assailant gives up the game. Charisse, a woman who had fled domestic violence, told me: “A lot of people out here are vile. I’ve had people kick me, spit on me, pour alcohol on me and light a lighter – I’ve had it all, trust me.”

Rape is a real concern. Homeless women are easy targets. Sexual assaults are horrifically common. Nothing is done, nothing can be done. By the time the girl has dragged herself to a police station the rapist will be on the tube home or tucked up in bed. This is why they tend to sleep during daylight hours.

I got an unpleasant taste of what it is to be seen as subhuman, not deserving of respect, only of suspicion and violence, during my time on the streets. In the early hours one morning I was sitting in a side street near Covent Garden with a guy I’d got to know and a group of his sleeping mates. Out of nowhere came a man in a suit – not a homeless man – reeking of booze and brandishing a piece of wood. He beat me down the right-hand side of my body and legs so hard that I was deeply bruised for 10 days. It was over in seconds. The men I was with were not surprised.

There is something else though, something equal to the violence, but somehow more cruel, damaging and subtle. Homeless people are belittled, diminished and treated with such contempt that it can drive them to take their own lives.

By about mid-morning every day I was dirty. My clothes were like magnets for filth: general city dirt accumulated from sitting on pavements and constantly being battered by polluted gusts of wind eddying up from the traffic. Sitting at everyone else’s knee-level is a not a clean place.

One particular time I went to a posh cafe to warm up, get a coffee and use the loo. I was eyed with great suspicion. My outward appearance had changed but I’d plainly not lost my sense of entitlement to a table in a fancy coffee shop. The waiter thought otherwise. He was cold and unfriendly. Unlike all the other customers I observed, he made me pay immediately, and not as I got up to leave. Instead of giving me verbal directions to the loo he actually came with me. An escort. He waited outside the door until I was done. It was horrible. It was cold and I went immediately into an Accessorize to buy another, thicker scarf. The shop assistant not only never took her eyes off me, she remained three paces behind me the whole time I was there. She saw a vaguely dishevelled, edgy and grubby-looking woman. A potential thief. Homelessness is much more than not having a home.

Now homeless people are criminalised, too. Antisocial behaviour orders are bits of paper quite a few homeless people have in their pockets. Typically, they’ll be handed out if the council wants a particular area “cleansed” – such as Regent Street in the tourist season or the main stations when international travellers are around. Darren told me: “We get arrested, go to court, get a massive fine and then we have to stand up and say, ‘Excuse me, your honour, I’ve got to go off and beg now, to pay this fine … and then I’m going to get caught begging and you’re going to fine me on top of the other fine I’m begging to pay …”

All the tremendously courageous, funny and damaged people I met during those weeks became my heroes. The weak and the poor are deserving of our kindness. And remember this – misfortune, bad decisions and tragedy are all that separate us from them.

• Tamsen Courtenay is the author of Four Feet Under (Unbound), a collection of 30 homeless people’s stories in their own words