It was 20 years ago to the day that a grisly discovery was made at Dover Docks.

Two decades later and had it not been for a similarly horrific find 63 miles away the fates of 58 Chinese migrants would have been largely forgotten.

The fact is it remains one of the greatest losses of human life on British soil but is missed off many such grim lists and is commemorated by only a few short paragraphs on Wikipedia and a small black and gold plaque in English and Chinese in the seaside town.

Rewind 20 years minus 18 hours and it would be freight supervisor Barry Betts and assistant Darren Bailey who were called over by customs officers to help unload Perry Wacker's lorry-load of tomatoes.

The pair cleared palletts of fruit from an unusually hot container, Wacker standing by and even laughing at one point when one was dropped.

But his expression changed to one of horror when he was told what Mr Betts and Mr Bailey had found.

Inside the trailer wooden screens had been uncovered by the men and beyond them, illuminated by Mr Betts' torch, was a "sea of bodies", first mistaken for fallen boxes.

The beam of light lit up a young topless man tapping on the side of the lorry to raise the alarm – it was only because it belonged to an unknown company that the vehicle was even stopped.

He was coaxed out and soon another man was dragged from the container. Su Di Ke, 20, and Ke Shi Guang, 22, would be the only two survivors.

Five hours earlier 32-year-old Wacker paid for his crossing in cash and climbed the stairs of the P&O Stena Line, tucked in to a meal and watched two films.

Downstairs his human cargo were panicking.

Wacker had closed the air vent before reaching the Belgian port of Zeebrugge to stop anyone spotting the people inside. Now the air was running out.

Those trapped in the back of the lorry began screaming, desperately trying to get help. Others frantically clawed through thousands of tomatoes and kicked at the wood panels.

For this ordeal each of the 60 would-be migrants had paid £20,000, a high price by anyone's standards but for them the equivalent of many years wages.

One man would tell Maidstone Crown Court during Wacker's manslaughter trial the following spring that his near-identical crossing a year earlier had cost his family £17,000 – an amount it would have taken him 24 years to earn in China.

The tragic events of June 18 2000 were set in course several weeks earlier in Beijing.

The 56 men and four women set off in small groups from the Chinese capital on their own passports, having obtained permission to travel to the Yugoslav capital of Belgrade.

They were escorted by minders from a snakehead gang – a catch all term for criminal groups who make millions from smuggling souls from poor Chinese communities into rich Western nations.

Once there they were taken to a safe house and given stolen Asian passports before being taken into Hungary and smuggled through Austria and France and in to the Netherlands where they were again taken to a safe house.

By this point they each had a code number instead of a name and were dressed in the same bleak uniform of a grey t-shirt and black trousers.

It was in Rotterdam where they were driven to a warehouse in two delivery vans and crammed into Wacker's lorry before being sent on the final stretch of their arduous journey accompanied by four buckets of water which quickly ran out.

Mr Ke and Mr Guang, the last loaded in to the lorry, recounted horrific details of their final hours during the trial, explaining how they were sealed in the boiling box for nine hours on one of the hottest days of the year.

Mr Ke told the court: "They started panicking after about two to three hours because the vent was shut and there was no air. Some people removed tomatoes and tried to kick open the doors. There was also a lot of shouting and screaming, but nobody came to help."

Through tears Mr Guang recalled how he had banged on the side of the lorry during the crossing but no help came.

After being dragged to safety the pair were taken to hospital suffering from dehydration and later given conditional leave to stay in the UK for four years.

At his trial Wacker denied knowing the true nature of his cargo, claiming he picked up the load for cash after losing his job.

"They [the police and customs] told me they found people in the back of the lorry ... I had no words, none at all. It was a heavy impact," he said.

Asked if he was concerned when he was stopped he said that he wasn't as he had been pulled up "25 or 26 times before", but admitted he was surprised when officials began looking in his lorry.

He told a jury he picked up the trailer from the docks in the Dutch city, finding the keys under the bumper, but was unaware of what was inside.

His friend Leo Nijveen – who himself had been fined £100,000 for smuggling 50 Chinese migrants in to the UK two months previously – had got him the job after hearing he was in desperate need of a pay day.

But the jury did not buy his story and convicted him of manslaughter and people smuggling. Mr Justice Alan Moses jailed him for 14 years.

Wacker's Chinese interpreter and co-defendant Ying Guo, of South Woodford, Essex, got six years for conspiring to smuggle illegal immigrants into the UK.

Nine members of the snakehead gang which organised the plot were later jailed.

It would have been optimistic at the time to have thought such a tragic incident would have had a serious impact on the trade in human lives – perhaps less so to think the atrocity was a one off.

But 19 years later at an industrial park on the other side of the Dartford Crossing the bodies of 39 Vietnamese men, women and children were found in the back of a lorry.

Again the mobile tomb had started its journey in Zeebrugge and again there was evidence it was part of a much larger fleet.

Essex Police investigations found there were several lorries linked to the one found in Grays which had made the same crossing to Purfleet in the weeks and months before the find.

Irish driver 25-year-old Maurice 'Mo' Robinson has since admitted manslaughter and there have been 14 other arrests around the world.

The true scale of human trafficking to the UK is almost impossible to calculate but one expert has told KentOnline there have probably been incidents like Dover and Essex before and they may happen again.