Migrants were given a 24-hour deadline to reach Europe as leaders announced anyone landing in Greece after midnight on Saturday would be swiftly deported.
A deadly scramble for the last boats over the Aegean to the Greek islands began after a €6 billion (£2.3 billion) aid-for-deportations deal with Turkey was agreed in Brussels.
Turkish police on Friday intercepted 3,000 migrants attempting to cross on land and sea in a major operation involving coast guard and helicopters, as Ankara at last showed a willingness to halt the human tide.
From Sunday morning, any asylum seeker who lands on the holiday islands including Kos, Lesbos and Chios will no longer be able to catch ferries to Athens, but will be swiftly interviewed by asylum officials or judges at new detention camps.
From April 4, once Greek law has begun, deportations to Turkey will begin with leaders hoping within weeks that the process will take no more than days.
Those that appeal their removal will be brought before Greek judges in rapid-fire court hearings, under an operation costing €20 million a month involving 4,000 staff.
David Cameron said that Britain will send further asylum experts and interpreters to join the task force. RFA Mounts Bay and Border Force cutters are already patrolling the Aegean.
“Britain will help. We have the expertise, we have skilled officials,” he said. “Today I’ve said that we stand ready to do more.”
“What we are doing here really is trying to create a harder border between Greece and Turkey, and in the end this benefits Britain,” he said.
“This is a herculean task facing us,” said Jean-Claude Juncker, the European Commission president.
“It is the largest challenge the European Commission has yet faced.” Many wonder how it can be achieved in a weekend, given the notoriously chaotic Greek administration.
Experts say the plan risks violating international law because Turkey is not a signatory to the Geneva Convention which guarantees basic standards for asylum seekers who are sent to other countries.
Turkey currently deports would-be asylum seekers back to the warzones of Iraq and Afghanistan, which is strictly forbidden in EU law.
“The deal is in accordance with the law, there can be no doubt about that,” insisted Mr Juncker, while Donald Tusk, the European Council president, said it was a “breakthrough” in the migrant crisis and said no-one would be forced back into danger.
“This is a dark day for the Refugee Convention, a dark day for Europe and a dark day for humanity,” said Amnesty International, adding the deal was “madness” that would only see deported migrants attempting fresh journeys to Europe.
“There is no better option,” said Ahmet Davutoglu, the beaming Turkish prime minister.
“It is also a historic day because we reached a very important agreement between Turkey and the EU,” Mr Davutoglu said.
“We today realised that Turkey and the EU have the same destiny, the same challenges and the same future.”
Mr Juncker’s officials dismissed fears that Saturday could see tragedies at sea as migrants pile into overloaded dinghies to reach Greece before the new regime kicks in, insisting that crossings have dipped over the 10 days of talks to cement the deal.
The highly controversial deal was struck after 24 hours of talks comprising a Turkish breakfast of white cheese, olives and cucumber, followed by a lunch of crisped potatoes with young vegetables, filet of brill with Swiss chard, and a kiwi and strawberry ring.
For every Syrian that is deported from Greece, one–starting with the most vulnerable–will be sent from the camps directly to EU states excluding Britain by a quota scheme up to a maximum of 72,000. Beyond that, the scheme will be deemed to have failed.
In exchange, Turkey will be handed €6 billion in aid, of which the UK will pay £500 million, amid grave fears of diplomats about it being “frittered” by the Turkish authorities.
In addition, Turkey will be granted visa-free travel to the EU’s Schengen zone from June providing it can meeting the 35 remaining criteria out of 72, something that few expect can be achieved.
Talks on Turkey’s entry to the European Union will also be accelerated with a new chapter on financial management being opened. Turkey’s preferred five chapters remain on the shelf due to a major stand-off over the recognition of the Cypriot government.
Nigel Farage, the Ukip leader, seized on the announcement, saying accession would drive British voters out the EU.
Mr Cameron insisted membership was “not even remotely on the cards” given that every country has a veto.
“In France they’ve said there’d have to be a referendum, and the last poll had 75 per cent of the French public against this move. I don’t think it’s relevant to this referendum campaign no matter how much Mr Farage would like to make it relevant.”
In northern Greece, officials pleaded with some 12,000 migrants at the muddy encampment of Idomeni to abandon any hope the Macedonian border would open and relocate to shelters run by the Greek army.
“I do not hesitate to say that this is a modern-day Dachau, a result of the logic of closed borders,” said Panagiotis Kouroublis, the Greek interior minister, referring to the Nazi death camp. “Whoever comes here takes several blows to the stomach.
Mr Davutoglu and his president, Recep Tayyip Erdogan, used the summitto rail against Europe’s toleration of the Kurdish separatist fighters, the PKK, blamed for terrorist attacks in Ankara but claimed by another Kurdish militant group, the Kurdistan Freedom Falcons (TAK).
A pro-Kurd demonstration took place outside the summit, infuriating the delegation.
“The snakes you are sleeping with can bite you any time,” said Mr Erdogan. “European countries are paying no attention, as if dancing in a minefield.”