Alongside a Frontex vessel flying the Union Jack, a group of Afghan men sat dangling makeshift fishing rods into the harbour at Mytilene. It’s over a year since EU and Turkish leaders signed an agreement to ‘end’ irregular migration across the Aegean. Brokered shortly after a cascade of border closures along the overland Balkan route, the deal says that migrants who cross to Greece after 19 March 2016, if their asylum applications are considered inadmissible, will be returned to Turkey. In exchange for gatekeeping at its end, Ankara would receive €6 billion, visa-free travel for Turkish nationals and a promise to fast-track EU membership talks.

By the end of 2016, only 1183 ‘irregular’ migrants had been returned to Turkey, but arrivals in Greece by sea have dwindled: around 2800 so far this year, a fraction of the 150,000 who made the crossing between January and March 2016. There are still 15,000 refugees trapped on the Greek islands, however – most of them on Lesvos.

On 18 March, the anniversary of the EU-Turkey deal, several hundred refugees and supporters turned out on the streets of Mytilene to protest against the accord. Most were single men from the island’s largest camp, Moria, toting placards calling for its closure, an opening of the borders and an end to deportations. Salim, a 47-year-old Syrian businessman from Daraa, showed me his official numbered wristband. In the past, he said, Europe kept its slaves with chains; now it keeps them with numbers. ‘The EU and Turkey are bargaining with us – it is a game for them. Well, I want to say: I am not for sale.’

In his seven months on Lesvos – months he says feel like 47 years – Salim has witnessed riots, sexual violence, self-harm, the deaths of a woman and child in a fire and half a dozen more during the winter’s fatal cold-snap. When camp officials declined to contact the family of a young Egyptian who had died of unknown causes, Salim traced them down online and broke the news over Skype. And when a young Syrian flew in from Sweden to see his grandfather, it was Salim who had to tell him that the old man had died the previous day. ‘Europe has killed my hope,’ he said. ‘I wanted to find a sky without bombs, so I went to Lebanon. But Lebanon was not safe, so I went to Turkey. And when Turkey proved unsafe, I came to Greece. And now I find here is not safe either – it is a prison.’

A report by Médecins sans Frontières documents a more than doubling in anxiety and depression among refugees on Lesvos since last March; a threefold increase in post-traumatic stress disorder and a spike in cases of psychosis, self-harm and attempted suicide. The morning after the protest, I heard that three Iranian men had been hospitalised overnight after attempting suicide in fear of being deported to Turkey. A young Syrian told me he was arrested and beaten by police after trying to smuggle himself to Athens in his mother’s suitcase. She had arrived in Greece a few weeks before him, the right side of the pivotal deal.

The deportation policy rests on the assumption that Turkey is a ‘safe third country’ where refugees can apply for protection. But this has been scoffed at by Amnesty International and Human Rights Watch, as well as legal scholars, who say that the policy violates the 1951 Refugee Convention and EU law. Deman Guler, a Turkish member of Lawyers for Freedom, points to the lot of the three million refugees already languishing in Turkey. Most of them are denied the right to work or education, are subject to threats and discrimination, and often forced into begging, prostitution or child labour. ‘I don’t believe such a large population can ever be returned from Greece,’ Guler told me. ‘If they are, Turkey has nothing in place to deal with it.’

After hearing the cases of two Syrian asylum-seekers, Greece’s highest court will soon rule on whether Turkey can be deemed a safe third country. A positive decision could open the floodgates for mass deportations from Greece; a ruling the other way could spell the end of the deal.

On Lesvos, meanwhile, the boats are still coming in. On the morning of the protest, a van in Mytilene turned out a pile of life-jackets, many of them children’s, from an arrival the night before. People will continue to flee, whatever paper bargains are struck in Brussels or Ankara.