How desperate would you have to be to put your child onto a rubber dinghy and wave them off to the mercy of the world? It beggars belief that people are doing it but they are. Some are parents who can afford only one fare so they buy a way out for their child.

It amazes me that, having lived through bombings and shootings and daily reminders of man’s inhumanity to man, they throw their children on our mercy, on the mercy of complete strangers.

It seems incomprehensible; or does it? On reflection we don’t have to think back too far to remember that we too parcelled up our children and sent them away from certain danger.

We hear a lot about the Kindertransport that brought Jewish children from occupied Europe to safe haven with families here. But we had our own refugees during that war: evacuees. In 1939, in just four days at the beginning of September, a staggering 3,000,000 people moved out of Britain’s cities following a government edict.

By the end of that week, one quarter of the population were living somewhere new. To save their children from the Luftwaffe’s bombing, parents in cities and towns tied a label around their children’s necks and, like parcels, put them on trains for the countryside in the guardianship of 100,000 school teachers. Many had no idea with whom they would be billeted. On arrival children were herded into village halls. Local families arrived to choose the ones they wanted. Back then, a distance of 50 or 100 miles might as well have been another country. The average family didn’t have a car and those that did had no petrol because of rationing. The children’s fathers were often away at war. Their mothers too may have been doing war work.

Parents had the comfort that the evacuation was encouraged by government and that the children would be with people whose culture and convictions were like their own. Even so, it was far from straightforward.

That was a more trusting age and some children paid the price of it. Actor Sir Michael Caine recalled being locked in a cupboard for a weekend while his adoptive parents went away.

Another evacuee, Sir Jeremy Isaacs, former general director of The Royal Opera House, Covent Garden, spoke about how difficult he found reconnecting with his parents when he returned home to Glasgow. He felt his bond with them had suffered a rupture that never entirely healed.

And yet such parents would have acted from the same impulse that has driven the parents of child refugees today; the impulse to save their child’s life.

Save the Children is working relentlessly to help the tens of thousands of unaccompanied minors who are making their way across Europe. It told me the story of a boy I will call Ali (to protect his identity).

He is 14 years old, from Afghanistan. After his father was killed in the conflict his grandfather told him to flee because he would be next. Over the past seven months he has been beaten many times and robbed of everything, even his clothes. He is in Serbia, having teamed up with other boys. An older one has taken him under his wing and together the band is headed for Sweden.

He knows that his mother and sisters later escaped but has no idea where they are in the world. One day he hopes to be reunited with them. To outside eyes, Ali and his newly acquired friends may look like the "young single men" said to make up a disproportionate number of migrants. But as any parent knows, a 14-year-old boy is a child in an elongating body.

Their age will make the decision to re-house them here a challenge. People will reach out to a doe-eyed toddler; a rangy teenager is a greater challenge but no less needy.

In the Sunday Times, the journalist AA Gill described meeting a boy he spotted in the "Jungle" camp in Calais. He wrote: "He has a handsome cockiness, the worldly, caged look of kids who fend for themselves." Then Gill’s translator asked the boy if he was frightened,

"And the mask of aged competence slips away revealing a heartbroken, terrified 11-year-old, thousands of miles from home, abandoned in the most desolate place the First World can construct."

There are worse risks than being beaten and robbed; worse fates than feeling lost and abandoned. Many of these children "disappear". Child labour, people trafficking and sexual abuse are real dangers.

So should we help them? Will we? David Cameron has been chewing over the idea for months. The giant-sized moral imperative for this father of small children is stacked up against the effect his decision might have on immigration. Ukip warns the children could be a Trojan horse: accept them and their families will follow. It will be true in some cases. But isn’t it a risk we must take?

Others point out that we have plenty of waifs of our own and the care we offer is sub-standard. Kent County Council, for example, says it can’t accept more unaccompanied children because all foster beds are used up.

The International Development Committee says it wants the UK to take 3,000 of the tens of thousands of unaccompanied children in Europe. The Daily Mail reports that the Prime Minister is more likely to take only hundreds and to take them from camps near Syria.

It would be a way to hedge his bets, to do something decent but to remain within the bounds of existing policy. It would be self-serving fancy footwork and it would be unworthy of us all.

How can we not take in thousands of these unaccompanied, at-risk children making their way across Europe?

During the Second World War an army of families opened their doors to evacuees. A few were unkind or abusive; about 12 per cent of children had an unpleasant experience. The vast majority were decent and welcoming.

The war was affecting everyone and all had to do their bit. That was how the country survived.

This time the war is not – thank goodness – on our soil. But we are in the backwash of a gargantuan humanitarian crisis. We may be rightly cautious about controlling our borders. The numbers arriving at the frontiers of Europe this month are six times greater than a year ago. We have no way of knowing whether we are at the beginning, middle or end of an influx triggered by conflict, climate change and disparities of wealth and expectation.

Irrespective of all of that, can we call ourselves civilised and leave children alone and undefended in the melee? It must be terrifying as an adult, more so as a child being trailed along by a parent. To be a child alone out must be as brutal as it is bewildering.

Would 3,000 families find it in their hearts to house a child? I think so if volunteers were requested. Would it cost Mr Cameron politically? Possibly, but only among the bigoted and mean-spirited. Will it cost him more if he doesn’t open up for children? Most definitely. If we leave those children to starve or freeze or "disappear" how can we call ourselves civilised?