A lorry container became a “tomb” when 39 desperate men, women and children suffocated as they were smuggled across the English Channel, a court has heard.

Temperatures in the pitch-black refrigerated unit reached an “unbearable” 38.5C (101F)as the Vietnamese nationals were sealed inside for at least 12 hours, jurors were told.

Unable to raise the alarm, one of them – a 28-year-old woman – wrote a text message that was never sent, saying: “Maybe going to die in the container, can’t breathe any more dear.”

Jurors were told the cost of being smuggled across the English Channel in the back of a lorry was some £10,000 per person.

Lorry driver Eamonn Harrison and Gheorghe Nica are on trial at the Old Bailey accused of the manslaughter of the 39 migrants who were found dead after the lorry arrived in Purfleet, Essex, in October last year.

The pair are also accused of being part of a people-smuggling conspiracy with another lorry driver, Christopher Kennedy, and Valentin Calota.

Opening their Old Bailey trial, Bill Emlyn Jones told jurors that it was a “sad and unavoidable truth” that some people were prepared to go to great lengths to come to the UK “for a better life”.

Their desperation made them vulnerable to exploitation by those who did not care about immigration law and saw them as an opportunity to make money, the prosecutor said.

Mr Emlyn Jones said the people-smuggling team had operated successful runs before the one in October last year that went “dreadfully wrong”.

He told jurors: “Obviously, any time you fill an airtight container with a large number of people, where they will be left for hours and hours, with no means of escape and no means of communication with the outside world – well, it is fraught with danger.”

On October 22 2019, 39 Vietnamese nationals – men and women, aged between 15 and 44, husbands and wives, mothers and fathers, sons and daughters – were loaded into the back of a lorry in northern Europe, he said.

Harrison drove them to Zeebrugge in Belgium, and unhooked his trailer where it was loaded onto a cargo ship bound for Purfleet, in Essex, jurors heard.

Another lorry driver, Maurice Robinson, then collected the trailer from Purfleet when it arrived just after midnight on October 23.

Mr Emlyn Jones said that by then it had been some 12 hours at least since “any meaningful amount of fresh air had been let into the sealed container”.

Robinson knew he had to check on the occupants, having been sent a message from his boss to “give them air quickly, but don’t let them out”, the court heard.

The prosecutor said: “Robinson drove out of Purfleet port and almost immediately stopped and opened the doors at the back.

“What he found must haunt him still. For the 39 men and women inside, that lorry had become their tomb.”

The refrigerator had not been turned on during the journey, meaning the temperature inside the trailer rose to 38.5C, Mr Emlyn Jones said.

What it must have been like inside that lorry does not bear thinking about. They had no signal inside the container, so could not call for help or alert the outside world to their plight

When Kennedy learned of the deaths, he told a friend it “must have been too many and run out of air”, the court heard.

Mr Emlyn Jones said: “What it must have been like inside that lorry does not bear thinking about. In fact, we do have some direct evidence of what the victims were going through, recovered from some of their mobile phones.

“They had no signal inside the container, so could not call for help or alert the outside world to their plight. But naturally, in desperation, they tried.”

Nica, 43, of Basildon, Essex, and Harrison, 23, of Mayobridge, Co Down, Northern Ireland, deny 39 counts of manslaughter.

Nica has admitted conspiracy to assist unlawful immigration between May 1 2018 and October 24 2019.

Harrison, Calota, 37, of Birmingham, and Kennedy, 24, of Co Armagh, Northern Ireland, deny the conspiracy charge.

Nica was said by the prosecution to be a “key player” in the smuggling operation.

On October 23 last year, he was in the area of Purfleet “primed” to meet the human cargo and was the second person Robinson called within seconds of the discovery of the bodies, jurors heard.

Previously, Kennedy had collected smuggled migrants at Purfleet and Calota had met them at a pick-up point nearby for onward transportation, it was alleged.

The court heard Robinson and haulage boss Ronan Hughes had pleaded guilty to the manslaughters and the people-smuggling plot.

Hughes, 41, who had a haulage company based in Co Monaghan, in Northern Ireland, played a “significant role” in organising the movement of his drivers, jurors were told.

Two other defendants have also admitted their part in the wider people-smuggling operation.

The victims were: Dinh Dinh Binh, 15, Nguyen Minh Quang, 20, Nguyen Huy Phong, 35, Le Van Ha, 30, Nguyen Van Hiep, 24, Bui Phan Thang, 37, Nguyen Van Hung, 33, Nguyen Huy Hung, 15, Nguyen Tien Dung, 33, Pham Thi Tra My, 26, Tran Khanh Tho, 18, Nguyen Van Nhan, 33, Vo Ngoc Nam, 28, Vo Van Linh, 25, Nguyen Ba Vu Hung, 34, Vo Nhan Du, 19. Tran Hai Loc, 35, Tran Manh Hung, 37, Nguyen Thi Van, 35, Bui Thi Nhung, 19, Hoang Van Tiep, 18, Tran Thi Ngoc, 19, Phan Thi Thanh, 41, Tran Thi Tho, 21, Duong Minh Tuan, 27, Pham Thi Ngoc Oanh, 28, Tran Thi Mai Nhung, 18, Le Trong Thanh, 44, Nguyen Ngoc Ha, 32, Hoang Van Hoi, 24, Tran Ngoc Hieu, 17, Cao Tien Dung, 37, Dinh Dinh Thai Quyen, 18, Dong Huu Tuyen, 22, Nguyen Dinh Luong, 20, Cao Huy Thanh, 37, Nguyen Trong Thai, 26, Nguyen Tho Tuan, 25, and Nguyen Dinh Tu, 26.

The trial before Mr Justice Sweeney is expected to go on for up to six weeks.