Who rescues migrants in the Channel?
The number of migrants crossing the English Channel by boat is small – it pales in comparison to those making the perilous journey across the Mediterranean – but there has been a small spike in crossings in recent months.
In 2018, the Home Office says 539 people attempted to travel to the UK on small boats. Of these, 434 (around 80%) made their attempts in the last three months of the year.
Of the 539, 227 (42%) were intercepted by the French before they made it to the UK.
Now, a Royal Navy patrol ship has been sent to deter them – but when people do cross, who is responsible for rescuing them?
A country's territorial waters stretch for 12 miles off its coast. After that, you're into international waters.
If a boat carrying people is found within national waters it's fairly clear-cut – that country has a duty to rescue them to a place of safety.
In international waters, it's slightly less clear and may vary on a case by case basis. But there is still a legal obligation to rescue those in distress and take them to a place of safety.
The stretch between Dover and Calais (the narrowest point) is entirely covered by territorial waters on either side but further down the Channel where it widens out, the waters outside of the two countries' territories are divided up into French and English search-and-rescue zones.
These rescue zones – which roughly divide the area of the Channel in half between the two countries – are coordinated by operations centres in Dover in the UK and Gris Nez (between Calais and Boulogne) in northern France.
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It's the responsibility of the authorities there to ensure that anyone in distress in these zones receives assistance. In reality, if people are in danger, any boat nearby will have a duty to rescue them.
Those picked up in the UK zone will be taken to an English port and those in the French zone to a port in France.
The French authorities told the BBC that they had stepped up patrolling in their zone since migrant crossings began to increase in October last year.
The patrols consist of naval craft belonging to the French customs authorities, the Gendarmerie or the French navy.
"Before October, we had only one patrol a day," says Ingrid Parrot, spokeswoman for the French maritime authorities in the Channel and the North Sea.
"Since the beginning of November, we decided to do night-time patrols with between two and four vessels, depending on the conditions at the time."
The French authorities say they intercepted an attempt to steal a fishing boat recently in the port of Boulogne.
Where can they seek asylum?
Under international law, people have the right to seek asylum in whichever country they arrive. There's nothing to say you must seek asylum in the first safe country.
However, under EU law there is a provision to allow asylum applications to be transferred to another member state.
The Dublin Regulation states that a person's asylum claim can be transferred to the first member state they entered.
In 2017 – the last year we have figures for – 461 people were transferred to the UK from another EU country under the Dublin rules, and 314 were transferred out of the UK.
The UK grants refugee status to those who are unable to live in their own country for fear of persecution because of race, religion, nationality, political opinion or other factors such as sexual orientation. A successful application usually allows someone leave to remain for five years with the opportunity after that to apply for indefinite leave to remain.
Entry into the original EU country must be proven – so if someone has travelled through mainland European without being fingerprinted and doesn't appear in the shared European fingerprint database, then they cannot be sent back.
If someone already has an asylum claim underway in another country, there will be a dialogue between those two countries about who is responsible.
If an asylum claim in another EU country has already been unsuccessful, the claimant has to prove that this decision was made unfairly or that their circumstances had changed since the decision was made.
Migrants coming from Calais, for example, are likely to have already made an application there according to immigration lawyer, Marcia Longdon.
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Children can also be transferred under Dublin Regulations to a member state if they have relatives living there who are capable of taking care of them.
If the UK leaves the EU with a deal, it will remain part of the regulations during the transition period. In the case of no-deal, it will stop being part of them on March 29.
In practice, a lot of border security co-operation between the UK and France is bilateral and governed by the "Le Touquet" border agreement, says Virginie Guiraudon, a migration specialist at the French National Centre for Scientific Research (CNRS).
"France is still respecting this agreement, even though President Macron had threatened during the Brexit campaign that France would pull out if the UK left the EU," she says.
The UK Border Force currently has five cutters and six coastal patrol vessels deployed – three in the Channel, two in the Mediterranean, one in Gibraltar and one remains in UK waters.
Home Secretary Sajid Javid said: "My focus continues to be on protecting the UK border and preventing loss of life in the Channel.
"For these reasons, the government has decided to deploy a navy vessel, HMS Mersey, to support our existing efforts. This will be an interim measure while the two Border Force cutters I have redeployed from abroad make their way back to UK waters."
A note on terminology: The BBC uses the term migrant to refer to all people on the move who have yet to complete the legal process of claiming asylum. This group includes people fleeing war-torn countries, who are likely to be granted refugee status, as well as people who are seeking jobs and better lives, who governments are likely to rule are economic migrants.
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