This ends our live coverage of the BBC's programming about how mass migration is changing the world. The day saw ex-MI5 chief Sir Richard Dearlove warn that the migrant crisis could spark a "populist uprising" in Europe.

Earlier, UNHCR special envoy Angelina Jolie Pitt said countries could not turn their back on the migrant issue - "If your neighbour's house is on fire you are not safe if you lock your doors." 

BBC coverage of the issue continues on radio and TV bulletins and the News website, and on Radio 4's The World Tonight (22:00), which reports from California on the changing patterns of immigration into the US.  

Watch Sir Richard Dearlove's warning that if Europe's leaders cannot inspire confidence in their handling of the migration issue they risk facing a "populist uprising". 

The chief technology officer for taxi-hailing firm Uber has told how he fled the Vietnam war in 1979 when he was 10 years old.

Thuan Pham described how he left his home in the middle of the night, crammed into a boat with hundreds of other refugees. 

They nearly sank, were robbed by pirates and then dumped on a deserted island where they had to build shacks to live in.

He told Ritula Shah on The World Tonight: "The experience did not scar me. If you live in a place where there is freedom and opportunity, you can make it."

Fellow panellist Shashank Joshi, from the Royal United Services Institute, argued that Sir Richard was not giving Europe enough credit for sanctions and arms embargoes against countries like Russia, Iran and China.      

As the session ended, panel chair Anne McElvoy pressed Sir Richard to reveal which way he would vote in the UK's referendum on EU membership. 

He did not answer directly but said he had been a convinced European and had not "quite given up on Europe". 

"Maybe we should give Europe one last shot" to deal with the migrant crisis, he said, "but if it doesn't deal with it, the consequences are lethal; they are politically lethal".  

Watch as Sir Richard Dearlove questions whether the EU is capable of a "massive  response" to the migrant crsis, reminiscent of the post-war Marshall Aid plan.     �`�`\�N

Times newspaper columnist David Aaronovitch suggested that each of Sir Richard's criticisms of the EU's failings "required more from the European Union and not less". 

Sir Richard suggested there was an alternative: for the "five major states of Europe" acting together but not "through the format of the EU with all the baggage that carries". 

Sir Richard ended his speech with a stark warning for Europe's leaders. 

"There are strong arguments on both sides but if Europe cannot act together to persuade a significant majority of its citizens that it can gain control of its migratory crisis then the EU will find itself at the mercy of a populist uprising, which is already stirring," he said. 

"The stakes are very high and the UK referendum is the first role of the dice in a bigger geopolitical game."

Sir Richard said terrorists could exploit freedom of movement and high levels of migration but "we should not conflate the problem of migration with the threat of terrorism".

He said: "With large numbers of people on the move a few of them will inevitably carry the terrorist virus.

"However, effective border control is probably not the most important part of countering terrorism. It does not pick up 'clean skins' [peole without police records] or those who are using different identities. 

"Good intelligence, drawing on human and technical sources and the analysis of data flows, is the key to effective counter-terrorism."

He said a number of the most lethal terrorists were already inside Europe, including the UK.

"They are already amongst us," he added.  

Image source, Jeff Overs/BBC

The former spy chief has more damning words about the EU's ability to meet a migration test which is "more serious" than that of 1945. 

"Failing to meet this challenge suggests that the EU in its present configuration of 28 vastly differing national interests, thrown into relief by the crisis, may well have outlived its historical role," said Sir Richard. 

"And the EU's inept response to the Balkan crisis, and to Ukraine's westward move away from Russia's former imperium is further evidence of an alliance of nation states struggling with its geopolitical role."

Sir Richard Dearlove has been sharply critical of the European Union's response to the scale of the migration crisis and says the impact is far-reaching. 

He said: "The EU's response has been hesitant and irresolute, complicated by the differing reaction of member states and the extent to which their national interests are affected. 

"To see walls and fences going up across Europe reminds me of the Iron Curtain which I crossed many times. It was always a sinister moment. 

"For the EU, however, to offer visa free access to 75 million Turks to stem the flow of migrants across the Aegean seems perverse, like storing gasoline next to the fire we're trying to extinguish (though for the moment the exodus has slowed)."

Sir Richard Dearlove, former chief of the British Secret Intelligence Service (MI6), says the context of the debate about migration is "heavily charged"  because of the referendum on UK membership of the EU. 

"We do stand on the threshold of having to make an historical choice and in my view time and circumstances are not propitious because of the migration crisis Europe faces."

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Image source, Getty Images

Thousands of people will try to reach Europe this year from countries like Syria and Iraq, taking the paths that hundreds of thousands of migrants before them have taken. That much we're familiar with.So what about this: the people who are choosing to go the other way? Jim Muir reports.  

Sarah Montague began the day on the Today programme telling how people are returning to Vietnam. But this interview with a woman who had to give birth at sea is a reminder of the flight of many Vietmanese people in the 1970s. 

When asked if he's more of an optimist than a pessimist, Lord Dubs tells Hardtalk's Stephen Sackur: "I think I'm more optimistic than pessimistic - that's why I do these things [campaigning]. I believe they do fully reflect what many people want. I think in Britain we have a humanitarian tradition which is still fantastic."

He says he believes that Sir Nicholas Winton, who organised the Kindertransport trains the saved him, would also be supportive of allowing more refugee children into the UK. 

Lord Dubs' proposal to amend the Immigration Bill to relocate and support 3,000 unaccompanied refugee children from other countries in Europe to the UK was rejected by MPs. 

Critics argued this would put more children in danger by encouraging them to travel to Europe unaccompanied.

When asked by Stephen Sackur if his arguments were ruled by sentiment, Lord Dubs replied that politics is "both head and heart" - not just one or the other.

Does the USA still have the welcome mat out for new arrivals? Nick Bryant reports from New York's Spanish Harlem, on the World Tonight at 22:00 on Radio 4.

In 1939, Lord Dubs says, Britain was the only country that took in the 'Kindertransport' children - children who escaped the Holocaust on trains from Prague organised by Sir Nicholas Winton. He is immensely grateful to the UK, he adds. 

Alf Dubs has been campaigning for unaccompanied refugee children from other countries in Europe to be granted entry to the UK. Here, he speaks to two young refugees from Syria.

Image source, Getty Images