On immigration sea patrol with EU border team
The south of England is particularly vulnerable to illegal immigration - the vast coastline provides a target for those wanting to slip into the UK.
The region is also home to busy airports and ports.
But where are illegal immigrants coming from right now and how do they get here?
European border officials say the biggest flow is from places like Afghanistan, Somalia and West Africa.
The current illegal gateway of choice into Europe is the Greek-Turkish border. Britain is often the favourite destination, where people have the chance of a better life.
I joined Italian sea patrols off the tiny, lush Greek island of Samos which, at its closest point, is less than one mile (1.6km) off the coast of Turkey, and which has become a major target for the trafficking gangs.
The price to get across here illegally is said to be 500 euros.
Traffickers use speedboats to get groups of immigrants on to the island; the traffickers then escape back into Turkish waters, where European patrol boats cannot normally enter.
Other immigrants have been found on crowded dinghies, some have sunk.
While out filming in the Aegean waters, a suspicious speedboat is spotted on the horizon.
It pulls into a cove along the rocky Samos coastline. A group of men are then seen fleeing up a mountainside.
"We have noticed four people who left the boat and started running up the mountains.
"Unfortunately we arrived a few minutes too late to intercept them directly," said Francesco Lasala, a captain from the Italian Coastguard.
"Normally, they take the boat back and drive it back to Turkey, this time they abandoned it and escaped."
The search starts for those who have run away.
Last year, an estimated 8,000 illegal immigrants were found by authorities on Samos. So far this year, nine people have been found dead.
The European border agency Frontex has 10 million euros worth of patrol operations going on in the area - with border guards from across Europe on look-outs from land and water.
Along the Samos coast, other signs of arrivals can be seen - a flat dinghy, rucksacks and other personal items.
Meanwhile there is no sign of the men who have just arrived, but the Italian team seizes their boat.
"During our patrol, we have to detect these suspicious targets in order to intercept them before they can come into Greek national waters and after that disappear on land and at sea," said Lieutenant Chiro Petrunelli, from the Italian Coastguard.
When smuggling boats are spotted, the Greek authorities have seen some dangerous tactics.
"There are several cases that the illegal immigrants, almost 80%, they destroy the boat or jump into the water so in that way they 'force' us to save them and so they secure their entrance to our country," said Metaxas Nikolaos, of the Hellenic Coastguard.
The traffickers operating here are part of sophisticated crime networks.
"They're very organised. For example, we have information right now about a guy in the Turkish shore who brings Iranians into Europe," said Panaziotis Kourdonourouris, from the Samos police department.
When illegal immigrants are arrested here by the Greek authorities, they are interviewed and most are given a police note telling them to leave voluntarily within 30 days.
Some use that as a way to disappear into Greece, into Europe. That is how some will have eventually ended up in the south of England and the rest of Britain.
Last year, more than 400 people were arrested across the south of England during illegal working and other immigration raids.
In Samos, the number of illegal immigrants being discovered has reduced dramatically this year, but hundreds have still been found.
The authorities are now reporting a huge increase further north at the Greece-Turkey land border.
So are these Frontex patrols just moving the problem?
Izabella Cooper, Frontex spokeswoman, said "to a certain extent yes" but that combating illegal immigration was a "very complicated task".
But she said as the "migratory pressure" had moved in the past four years from the western Mediterranean and Canary Islands to Greece, Frontex had been been able to gather important information about the networks behind human trafficking and how to counter them.
The men we saw on the hillside in Samos were eventually arrested by police. It turns out the boat seized was one police had been hunting for some time.
But the fight against illegal immigration is far from over in these Greek waters.