“Are they shouting hello?” “No, I think they’re shouting for help.”

It took us a few minutes to realise that the ever-so-friendly family waving at us from the sea shore were about to drown. Surprised by a fast incoming tide, the rocks they were standing on had become an island and the water was rising.

We called 999.

It was the first time I had seen a helicopter. The noise was immense as it hovered and then lowered and relowered a man on a rope until he had plucked each imperilled human into the hold.

It was all so perfunctory. As though they did this every day. Maybe they did.

What strikes me looking back is what they didn’t do.

They didn’t throw down armbands for the family to put on just in case. They didn’t drop planks of wood for a raft to be built. They didn’t jump into the water and swim around to show them how an escape could be made.

Of course they didn’t. It was a crisis. And they knew would what work. So they did it. Who would do otherwise? Surely all of us – faced with any sort of crisis – would focus 100% of our energy and resources on what is most likely to work? Wouldn’t we?

Does knife crime count as a crisis? Over 100 young people lost their lives in the last five years, so I think it should.

Maybe though – in this case – we don’t really know what works? No, that’s not the case – the evidence is pretty clear. If we want less children to die we need more mentoring, more therapy, more family support and more police in the areas where violence is high.

So surely that’s what we do. Isn’t it. We wouldn’t do unproven things here, would we? It’s a crisis.

Except we do.

Last year, the charity I lead – the Youth Endowment Fund – published new research that showed that three of the main methods we use to reduce youth violence are pretty much unproven. There is no clear evidence that putting police officers in schools, providing ‘bins’ for people to anonymously surrender knives or running anti knife-crime adverts saves any lives.

Despite this, over the last three years, this country has spent time and money on these three approaches. Maybe the country is just flash for cash at the moment?

But hang on, just because there is no evidence yet that these things save lives – that doesn’t mean case closed. Maybe they do work and we just don’t have the evidence yet.

That’s possible. There have not been really rigorous trials to see whether these things work. (The charity I lead is keen to conduct some just in case these are in fact great solutions.)

But – here’s the thing. There is also no rigorous evidence that throwing planks to make a raft with at people drowning at sea is a bad idea. But we don’t do it. Why not? Because we expect the coastguard to focus on stuff that’s known to work.

In a crisis, we expect the emergency services to do what works. We expect an ambulance to arrive with a defibrillator not a pot of leaches, a police car to pull up with handcuffs not a tickle stick and a helicopter to bring a winch not some planks.

Don’t the children at risk on streets deserve the same?

If you want to know what works to save lives, the YEF Toolkit summarises 2000 trials. It’s as though Which Magazine have produced a magazine on how to reduce violence. www.youthendowmentfund.org.uk/toolkit