The Channel migrant story has dominated the news in recent days – so what has been going on? Here's an in-depth guide.
:: Why has Home Secretary Sajid Javid called the situation a "major incident"?
There has been a sharp rise in December in the number of migrants being picked up by UK authorities while trying to cross the English Channel in small boats such as dinghies.
Scores of people have been intercepted, including 12 men on two boats who were brought to shore at Dover last Friday. Forty migrants were detected on Christmas Day.
There are fears it is only a matter of time before there is a migrant death in the Channel from a capsized dinghy.
:: Why has there been an increase in the number of migrants trying to cross the Channel?
It is believed the recent mild weather and calm sea conditions have led to more attempted crossings.
Also, smuggling gangs could be trying to exploit the holiday period, where there may be fewer border staff on duty than usual.
:: Who are the migrants?
Many of them are thought to come from Iran and others from war-ravaged Syria. Some have said they would rather die trying to make the sea crossing to the UK than return to France.
It is reported that one reason for the increase in Iranians is the effect of sanctions imposed on their country by the US.
Iran's economy has been squeezed and many young men are struggling to get work, despite being well-educated.
There has also been an increase in the number of French police raids on Calais camps, dispersing the inhabitants.
:: What is the UK government doing to try to stop the migrants' Channel attempts?
Mr Javid, who is returning to work early from a family holiday, declared a "major incident" on Friday and said the situation was "of grave concern".
He said people were "gambling their lives in reckless attempts to reach the UK in unsafe boats and treacherous conditions".
Mr Javid has appointed a "gold commander" to oversee the situation and give daily updates.
There are currently two Border Force cutter boats available for patrol but there have been calls, including from Dover MP Charlie Elphicke, for similar UK vessels to be brought back from the Mediterranean to intercept traffickers' dinghies.
A spokeswoman for the Immigration Services Union (ISU), which represents Border Force staff, said the two ageing cutters available were "woefully inadequate".
Mr Javid said he was keeping the number of Border Force vessels in the Channel "under close review", but admitted there was "no one easy answer" to the situation.
He is due to speak to his French counterpart on Sunday.
:: Could the Royal Navy help?
Some MPs want the navy to be deployed.
Defence Secretary Gavin Williamson said the armed forces were ready to offer help if needed.
He told The Sunday Telegraph: "We have not had any requests as yet but if the Home Office is in need of armed forces support then our navy, air force and army stand ready to assist."
2:55:: What is France doing to crack down on its side?
The head of the National Crime Agency-led Invigor organised immigration crime task force, Chris Hogben, said UK-French co-operation has led to dozens of attempted crossings being prevented.
He said three suspected "facilitators" were arrested and charged in France last week and will face trial in the new year.
He added: "Over the last three weeks, our French colleagues have disrupted numerous attempts, recovering at least 95 migrants including nine children, and arrested seven people caught attempting to facilitate these crossings."
However, a volunteer who works with migrants described how difficult the French coastline is to police.
Maya Konforti of the charity Migrants Inn said there were around a dozen spots between Boulogne, Calais and Dunkirk, along a 30-mile (48km) stretch of coast, which would be suitable launch spots for migrant boats.
2:39:: Will there be more attempted crossings in the near future?
Mr Hogben has warned more crossings are "likely" early next year.
He said: "Working with our French partners, we would anticipate further arrests over the coming weeks and also more attempts to reach the UK are likely."
:: Could Serbia be linked to the current situation?
A Serbian refugee organisation claims the migrants arriving in the UK are among thousands who flew to Serbia after the country started offering visa-free access to Iranians in August 2017.
The move was to increase tourism and trade between the countries but the visa scheme led to claims it was being abused by migrants seeking access to western Europe.
Around 40,000 Iranians are believed to have flown to the Balkan nation by the time the scheme ended in October.
Reports said direct flights from Tehran to Belgrade were full when they arrived in the Serbian capital but were empty when they returned.
2:57:: How have other countries tried to tackle the migrant situation?
Italy's new right-wing government has taken a noticeable hard-line against migrants.
A bill passed in September will make it easier to expel migrants and strip them of citizenship.
The new legislation is "a step forward to make Italy safer", interior minister Matteo Salvini said, adding it would help Italy "be stronger in the fight against the mafia and (people) smugglers".
His government has moved to stop rescue boats actively saving migrants at sea and bringing them to Italy's shores, arguing that other European Union countries need to do more.
Hungary has also taken an anti-migrant stance.
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Its parliament has passed a series of laws that criminalise any individual or group that offers to help an illegal immigrant claim asylum.
The legislation restricts the ability of non-governmental organisations (NGOs) to act in asylum cases and was passed in defiance of the European Union and human rights groups.
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