The Tube doors opened and I stepped in, instantly struck by the rather pungent odour of fried food and wine.
At least half a dozen takeaway boxes had been strewn about the carriage floor, along with shards of glass from a broken bottle.
Some of the white wine it once contained had been soaked up by discarded newspapers, creating a soggy mush that the feet of oblivious passengers had spread around.
I travel on the Underground every day but I’d never seen such carnage. I took my seat alongside other passengers and we sat in silence, staring at the mess.
I was quietly seething that people would treat public transport like a tip; I wondered when a cleaner might be alerted and come to pick up the broken glass, if nothing else.
Then I had a lightbulb moment: rather than getting angry, why didn’t I do something?
It occurred to me that all of us in that carriage, despite disapproving of the mess and stench, were displaying a phenomenon known as the ‘bystander effect’.
Not one of us was prepared to make the first move. We were all waiting to take our lead from someone else.
I first learned about the bystander phenomenon, albeit in very different circumstances, as a trainee psychiatrist. A lecturer told us about the tragic case of Kitty Genovese, who was stabbed to death in Kew Gardens, New York, in 1964.
Subsequent investigations concluded that a total of 38 people saw the prolonged attack or heard her cries for help — but did nothing to intervene.
The case spawned a number of psychological experiments which explored the bystander effect in more detail and discovered it was widespread.
Various factors contribute to such behaviour.
During an incident, people will wait to see if others get involved — it’s called ‘diffusion of responsibility’.
In the aftermath, individuals at the scene often say that they did not feel sufficiently qualified or important enough to be the first person to get involved.
Such inaction is also partly down to ‘pluralistic ignorance’ —the idea that, since no one else is reacting or responding, this must be the correct course of action.
Intriguingly, studies have shown that once people are aware of the bystander effect, they are less likely to be affected by it.
Remembering this put me on the spot. So I picked up a newspaper from the floor and began clearing up the broken glass. The reaction of other passengers was astonishing. A woman opposite said she’d help. Then a man produced a plastic bag to put the rubbish in. Further down the carriage, another man started picking up papers.
The train stopped at a station, and someone got in. He stood for a few moments, watching us all, before pitching in himself.
By the time we reached the next stop, the carriage was clear of litter. I got off with three bags of rubbish, which I handed to a bemused cleaner standing on the platform.
Aside from the environmental impact of littering, I’m interested in its psychological aspects — how litter on the streets communicates an acceptance of decay, and a lack of interest in doing anything about it.
This has been termed the ‘broken windows’ theory — the idea that visible signs of crime, anti-social behaviour and civil disorder create an urban environment that encourages further crime and disorder.
But it also provides an opportunity for socially conscious and civic-minded people to make a difference, if only we can learn to overcome the bystander effect and realise that we can be an agent of change.
It’s annoying and frustrating that people can be so selfish and careless, but at least my fellow Tube passengers and I responded positively that day — in the end.
On a personal level, it was satisfying to consider that, rather than grumbling, I’d taken action. And it was the push I needed to sign up to the Mail’s Great British Spring Clean campaign, organised with Keep Britain Tidy. In fact, I’ve already begun to pick up litter. I do hope you’ll join me.
The number of children being treated for eating disorders on the NHS has risen by 50 per cent, according to the Children’s Commissioner’s mental health report.
This should worry every parent, because the situation is only going to get worse.
The proliferation of smartphones means that most of us — particularly the tech-savvy young — have constant access to a camera.
This has fuelled the development of an increasingly image-obsessed society in which Facebook, Twitter, Snapchat, Instagram and other social media platforms encourage us to share carefully posed photographs of ourselves.
And, thanks to photoshopping apps, young people in particular are also being bombarded with images that appear natural but have, in fact, been carefully manipulated.
This culture puts youngsters under increasing pressure to conform to unrealistic standards of beauty, and makes them more likely to diet. In those with underlying psychological and emotional problems, a diet can become an eating disorder.
Social media companies have a responsibility to flag up images that have been digitally manipulated. Until they do, the epidemic of anorexia and bulimia will continue.