Family reunion routes – that is, those granted refugee status in the UK being able to apply to bring relatives to join them – have been drastically curtailed.

The UK gave protection – grants of asylum, humanitarian protection or alternative forms of leave and resettlement – to 18,519 people in the year ending June 2019, according to the most recently available figures.

However, it is relatively hard to secure asylum in the UK, which hosts less than 1 per cent of the world’s refugees.

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Furthermore, the hostile environment policy, including the UK’s use of immigration detention (it is one of the only countries in the world where the period of detention is not capped), is likely to have deterred some people from wanting to seek asylum at all for fear they will end up in purgatory.

The Dublin regulation, an EU law which states that an individual is eligible to be given asylum only in the first safe country they arrive in, encouraged people with good reasons for wanting to travel to the UK – for example, good command of the language – to attempt to do so by dangerous back door routes, often facilitated by ruthless people smugglers.

The Joint Council for the Welfare of Immigrants said: “Nobody should be in any doubt that the ultimate responsibility for these deaths lies with government policy, which has deliberately shut down safe and legal routes to the UK.

“We need more than empty expressions of sadness and shock from [Home Secretary] Priti Patel and [Prime Minister] Boris Johnson. We need a commitment to opening safe and legal routes to the UK and quick decisions for people seeking to make a better life for themselves in the UK. People move – they always have and they always will. Nobody should have to risk their life to do so.”

The 39 people found dead in the back of a truck near London were Chinese, ITV News and BBC reported on Thursday, as police questioned the driver of the vehicle who was detained on suspicion of murder.

Paramedics and police found the bodies of 38 adults and one teenager early on Wednesday in a truck container on an industrial estate at Grays, about 32km east of the British capital.

Alongside the murder inquiry, a parallel investigation has begun to examine whether organised crime networks – widely believed to be behind a recent surge in people-smuggling operations seeking to bring migrants to the UK – played a role.

The UK’s National Crime Agency has responsibility for tackling what it calls organised immigration crime. This stands apart from modern slavery and human-trafficking because it involves consent on the part of the individual travelling, while the latter involves coerced movement across borders. However, there is an obvious overlap and the incident in Essex could be either of the two.

A range of methods are used in organised immigration crime, including clandestine entry from near Europe, air-facilitated migration, use of false or fraudulently obtained documents and abuse of legitimate entry and leave to remain.

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In 2018 new migrant camps emerged in the Grande-Synthe and Puythouck Lake areas near Dunkirk, where organised crime gangs are known to be active, recruiting migrants for onwards movement to the UK.

Juxtaposed border controls remain the main targets for clandestine entry into the UK. These controls are part of an arrangement between the UK, France and Belgium whereby immigration checks on certain cross-Channel routes take place before boarding a train or ferry, rather than on arrival.

In 2018 the number of Eritreans detected at juxtaposed controls increased notably, with Eritrean nationals found concealed in refrigerated lorries and containers, probably indicating growing levels of organisation.

The top 10 nationalities of undocumented people found at juxtaposed controls in 2018 were Eritrean, Iraqi, Afghan, Iranian, Albanian, Sudanese, Vietnamese, Pakistani, Syrian and Ethiopian.

What could be done in the UK to reduce the chance of individuals attempting such risky journeys? Refugee and asylum seeker rights campaigners have been calling for an extension to refugee family reunion rules to include a wider definition of family, allowing individuals safely based in the UK to bring family members to join them.

There have also been calls for the resettlement programme for Syrian refugees, which is run by the UN refugee agency, to be extended to other countries.

The Essex case is reminiscent of the 71 migrants who were found suffocated in an abandoned truck on an Austrian motorway in August 2015, at the height of Europe’s refugee crisis.

In 2000, police found 58 Chinese migrants dead in a container truck at the southeastern English port of Dover.

The following year, a Dutch driver was sentenced to 14 years in jail for manslaughter. The immigrants, who paid a smuggling gang US$26,000, suffocated to death after the driver closed the air vent on the truck during a five-hour ferry ride across the English Channel.

Additional reporting by DPA and Associated Press