I once cried on the tube in London. Tears dripped down my face, an inconsolable stream barely contained by my wet hands.

I no longer remember what I was crying about. But I do remember the kindness of a hunched Nigerian woman, dressed in her Sunday best, who from her seat opposite, was watching me carefully. While everyone else in the carriage pretended not to see, she looked directly at me with widened eyes.

As the train pulled into a station, she pulled a handkerchief from her pocket, and laid it on my knee. She grabbed and squeezed my hand. “This too shall pass,” she said with a fierce certainty. And then vanished between the closing doors, off to continue the rest of her day.

Even now, several years on, thinking back to that day makes me emotional. She recognised that she could solve nothing except letting me know that nothing could be solved. Which is why she was unique. It’s not that everyone else on the tube didn’t see my crying. It’s that the rest of them didn’t know what to do about it. So they did nothing at all.

It’s not that everyone else on the tube didn’t see my crying. It’s that the rest of them didn’t know what to do about it.

I was reminded of it this week when Theresa May made her announcement to tackle mental health issues in Britain, starting with a package for schools.

The speech she made on the issue was superb. It highlighted the right statistics – the one in ten children with a diagnosable problem, the high suicide rates among young men.

But her package of support for schools only deals with the first part of the problem: spotting the issue. And, to be honest, I don’t think teachers need all that much help. When you spend your days with children you know the difference between a kid “being a bit mental” (zany, that is) and those who are actually troubled.  You know who needs more help to stay attached to reality or to get through the day without harming themselves.

The problem, therefore, is not that teachers fail to see mental illness. It’s that there isn’t a whole heap they can do about it. As our cover story this week shows, the average number of days children wait for referrals is now at 28 days – and this is only for serious cases, such as children at risk of physical self-harm. Budget cuts mean schools are also increasingly struggling to provide follow-on services, such as counsellors or welfare officers.

Like the people on the tube, it is not that teachers cannot see the disturbed children, it’s that they don’t know what to do about it.