This is the story of two youngsters who were sent, unaccompanied, by their parents to seek refuge in a foreign land.

One of them, a 20-year-old male, was arrested a few months after his arrival and locked up in a prison camp. The other, an 18-year-old female, found work with family friends. Her mother, who had to stay behind in their home country after being refused entry into the UK, was later murdered by a government death squad.

The two youngsters were refugees. If they had stayed in the country of their birth, they would almost certainly have been killed. I am glad that they managed to get out, even though millions more didn’t.

Why do I tell their story now? First, because we have supposedly just been marking World Refugee Day, although you could be forgiven for having missed it. Refugees aren’t exactly flavour of the month these days.

And second, because those two youngsters were my parents, who escaped from Nazi Germany in 1939. They both later joined the British army and served in a top-secret military intelligence unit, which is where they met.

Let us not, however, mythologise the past. Whatever you may have heard, refugees have rarely been welcomed with open arms. In the years before the Second World War, an estimated 70,000 Jewish refugees were granted asylum in the UK – but another 500,000 who applied for entry were unsuccessful. Among them was my grandmother.

Now fast forward to today. President Trump believes migrants from Mexico and central America are ‘infesting’ the US. His choice of words is chilling, given that ‘infesting’, as you don’t need me to tell you, is something normally associated with vermin.

During the presidential election campaign, he said of Mexican migrants: ‘They’re bringing drugs. They’re bringing crime. They’re rapists.’ (And then, as an afterthought, as if he had shocked even himself by the violence of his rhetoric, he added: ‘Some, I assume, are good people.’)

Honduras and El Salvador, from which many of the migrants have come, just happen to be the two countries with the highest murder rates in the world. If you or I were parents there, we too would be prepared to risk everything to find a place of safety for our children. Yes, even if it meant crossing a border illegally and risking arrest.

But that doesn’t matter to Mr Trump. Compassion is as foreign to his psyche as it is to the Hungarian prime minister Viktor Orbán, who has just introduced legislation to criminalise any individual or group that offers to help asylum-seekers, or to the populist Italian interior minister Matteo Salvini, who has refused to allow ships carrying desperate migrants from north Africa to dock at Italian ports and has called for ‘a mass cleansing, street by street, piazza by piazza’ of Italy’s Roma population.

And while we’re pointing fingers, let us not forget the horror that is the Yarl’s Wood immigrant detention centre in Bedfordshire, where more than four hundred people are being held in conditions described by the Green Party MP Caroline Lucas after a recent visit as ‘psychological torture’. Those who live in glass houses…

Of course, I’m sympathetic to refugees and asylum-seekers. With my background, how could I not be? But what I find hard to understand is why hostility towards refugees and other migrants still seems to be so widespread.

Did refugees cause the global financial crisis a decade ago? Was it refugees who slashed public services, closed libraries and under-funded the NHS? Of course it wasn’t.

According to the UN, there are now more refugees than at any time since the end of the Second World War. Why? Because more are fleeing from conflicts – including those in Syria, Yemen, Afghanistan, Myanmar, Democratic Republic of Congo and South Sudan – and from what the 1951 UN Refugee Convention calls ‘a well-founded fear of being persecuted for reasons of race, religion, nationality, membership of a particular social group or political opinion.’ Millions more are fleeing from grinding poverty, in part as a result of climate change, and the fear of violence at the hands of drugs cartels.

No one suggests that all countries should throw open their borders willy-nilly to all who wish to enter. But surely the richest countries in the world have a clear moral duty to devise a fair, humane system for offering sanctuary to those who are in fear for their lives.

If Hungary, for example, refuses point blank even to consider any EU proposal to take in refugees, perhaps Mr Orbán could be reminded that belonging to the European Union involves responsibilities as well as benefits. Perhaps he has forgotten that when Hungary joined the EU in 2004, it signed up to the so-called ‘Copenhagen criteria’: to preserve a democratic system of government, to guarantee human rights and a functioning market economy, and to accept the obligations of EU membership.

The demonisation of refugees – and of migrants in general – is a stain on the modern world. For President Trump, targeting them is a cheap, cynical ploy to energise his core supporters. The same goes for Viktor Orbán in Hungary, Matteo Salvini in Italy and populist demagogues everywhere. What could be easier than stirring up hatred of foreigners?

Even in once-liberal Sweden, growing support for the anti-immigration Sweden Democrats party now means that they could well end up holding the balance of power after elections later this year. All in all, it is a deeply depressing picture.