Four men have been jailed over a people-smuggling operation in which 29 Vietnamese nationals, including 17 children, were crammed into a dilapidated yacht and transported from France to Cornwall.

Astonished port workers in the fishing harbour of Newlyn phoned police as the Vietnamese men, women and teenagers were loaded into a windowless van and driven away. Officers tracked the van and intercepted it on the M5 motorway in Devon more than 100 miles away.

All except one of the adults subsequently vanished and police fear they may have fallen into the hands of organised crime groups and could be being forced to tend cannabis farms or work in the sex industry. Some of the children are being cared for in the UK but others have also disappeared.

Among the four sentenced are Frank Walling, 73, and his cousin Glen Bennett, 55, who are both from Lancashire and have served long jail terms for drug smuggling. Walling skippered the yacht while Bennett was his crewmate.

Walling’s previous exploits have included an ill-fated mission to smuggle cannabis from Morocco to the UK on a leaky boat. At one point during this mission he hitched a lift with a tourist on a pedalo when he had to get to shore to make a call and then ran aground in the River Lune in Lancashire. He has also been jailed in Portugal for smuggling. Walling and Bennett were both jailed for four and a half years.

Friends Keith Plummer, 64, and Jon Ransom, 63, from Kent, were in charge of transporting the Vietnamese people from Cornwall by road, possibly to south-east England. They have long criminal histories of burglary and dishonesty. Plummer was sentenced to 40 months and Ransom to four and a half years.

The police accept the four did not head the operation but believe it may have been controlled by a person known simply as Mark 3 – a name found in the memory of one of their phones.

Officers suspect this may not have been the first time some of the gang members had smuggled people into Cornwall but they were caught this time because they mistimed the trip and arrived in daytime rather than under the cover of darkness.

DI Glenn Willcocks of Devon and Cornwall police said: “We hope the sentencing serves as a reminder that people are not commodities to be handled like cattle with total disregard for their health and safety.”

Images of the yacht show that its hull was stained and the interior cramped and dirty. There were cans of beans and packets of noodles in its cupboards, a filthy sink and one blocked toilet.

Willcocks said: “The four risked the lives of 29 men, women and children. They were motivated only by monetary reward – and thankfully no one paid the ultimate price.”

Truro crown court was told that the yacht, the Johan Sebastian, sailed from Roscoff and arrived in Newlyn on the morning of 12 April 2019.

Newlyn fish market worker Dale Frisk observed the Vietnamese people jumping off the boat. “They were diving over the wall and into a van,” he said. Frederick Bates, who works on the harbourside mending fishing nets, added: “This was a really unusual sight, especially at 7am.”

A service station worker, William Ives, who served Plummer and Ransom hours before the yacht arrived said he believed he had seen them before, suggesting this was not their first trip to Newlyn.

People-smuggling checks at UK ports inadequate, hauliers say Read more

Police found 15 sea charts on the vessel showing different parts of the coasts of northern France and southern England, again hinting this may not have been their first such operation.

Most of the Vietnamese people told police and immigration officials they had come to the UK to better themselves and had journeyed through Europe before the trip across the Channel. One had paid £1,500 for the journey.

Sentencing the four, Judge Robert Linford said they had traded in human misery and exploited “hapless” people. He said the operation was well organised, though not particularly sophisticated.

The four men were convicted under section 25 of the Immigration Act: assisting unlawful immigration.