Video report by ITV News Correspondent Emma Murphy

Four years ago I stood on a beach on the Greek island of Lesbos and watched incredulously as a flotilla of rubber boats, so overloaded they were barely above the waterline, made their way to the shore.

Onboard were a mass of the desperate, terrified, relieved and exhausted. Children were thrown to outstretched arms of strangers, men and women stumbled out, weeping, cheering or silently staring at the water they had thought might kill them.

One man asked in perfect English: 'What country am I in?" It was a question and an image I shall never forget. They were all Syrian and had sought the dangerous journey to distant shores in the hope of life.

Watch Emma Murphy's 2015 report from Lesbos below

It was the start of the European migration crisis and those people make up some of the 70 million displaced spoke of in the United Nations report published on Wednesday.

Almost as quickly as that group arrived, they were gone from the beach - their first steps towards a different future.

A few lifevests were all that was left - on this occasion their role successfully achieved.

Now those few vests number thousands. So much so, there is a lifevest mountain on Lesbos. Each one brought ashore on the living or the dead.

Since then over a million migrants have arrived in Greece from trouble spots around the world. Some left here for other countries, some stayed, others remain in camps.

Vast swathes of lifevests were discarded near to the beach in Lesbos. Credit: ITV News

And still they come - just this month over a thousand have arrived on the island. That is a spike in numbers which concerns many.

Migration is the issue of this century - it has polarised politics, brought the best and worst out of communities. It is not going away. There are too many failed and fragile states from which to take flight. It will take a triumph in joined up global foreign policy to truly tackle migration. So far there seems to be neither will nor way.

The lifevest mountain will keep growing in Lesbos.