A mum of four who was caught with her boyfriend smuggling 12 Vietnamese illegal immigrants, including teenagers, into the UK hidden inside a van-load of stacked tyres has been jailed for two years and nine months.

Katy Bethel, who was six months pregnant with her youngest daughter - described by a judge as 'good cover' - when the five women, four men and three children aged between 40 and 16 were discovered by border control officials concealed in the Mercedes Sprinter, sobbed in the dock.

A judge told her the fact she had children could not spare her from prison as a deterrent sentence was necessary to prevent human trafficking gangs from preying on women with similar backgrounds.

Described by her barrister as naive, 28-year-old Bethel was a front passenger in the van while her then boyfriend and father of two of her children, Aaron Harris, was driving.

The illegal entrants were spotted when an officer at the UK control zone in Coquelles, France, saw a pair of jean-clad legs sticking out of the piled-high tyres.

Bethel told a court she had no idea the illicit 'cargo' was concealed just feet from where she was sitting, and claimed she and Harris had gone on a last-minute cross-Channel daytrip to stock up on alcohol to celebrate the impending birth of their child.

However, a jury at Maidstone Crown Court in Kent heard no booze was found in the van and Bethel was convicted by a majority of 11 to one of assisting unlawful immigration.

The jury of 10 women and two men deliberated for longer than it took to hear all the trial evidence.

Bethel was in tears at the verdict last month and sentencing was adjourned until today so she could make care arrangements for her four daughters aged between eight years and one.

Harris, 28, admitted the same charge at a previous court hearing and was jailed for five years.

According to his Facebook page, Harris once worked as an assembly line worker for Channel Tunnel Rail, and when arrested he told officers: "This is the daytrip from Hell. I'm usually a lorry driver not a criminal."

Bethel and Harris are no longer together and sat wide apart in the dock.

The court heard the couple, both from Gillingham in Kent, were stopped at about 9pm on July 4, 2015, as they headed home via the Eurotunnel from Calais.

Harris told officials everything in the works vehicle belonged to him, except the tyres which were his boss's. Bethel claimed they had been to the beach.

The illicit concealment was then discovered in its cramped conditions when Harris was asked to open the rear doors.

Prosecutor Michael Morris said: "Upon opening the doors the officer saw what appeared to be jeans or jeaned-legs within the tyres.

"He asked 'What's that then?' and Aaron Harris replied 'How did he get in?'

"There were 12 Vietnamese nationals concealed in that load of tyres. All were illegal entrants trying to get into the UK.

"The tyres were loaded on top of them so they were in the centre of the piles of tyres."

Judge Philip Statman remarked the illegal immigrants were in 'a very sorry state, distressed and looking pretty much down at heel'.

He also stated that Bethel's pregnancy was to be used as 'good cover' for the scam.

The prosecution case against Bethel was that she 'knew or had reasonable cause for believing' she and Harris were carrying out a breach of immigration law.

Mr Morris told the jury that she did not need to know the nationality, age or any other detail about those being smuggled into the UK, to be guilty of the offence.

Almost 70 calls and texts were made between Harris's and Bethel's phones and an unknown number during the four-hour trip but Bethel said she did not pay attention to what her boyfriend was doing or saying as she felt sick and tired from her pregnancy.

Her phone was also used to make numerous internet searches for van hire.

She denied her account of what happened was 'nonsense' or that she was trying to 'wriggle out' of any blame.

When questioned during her trial as to why no booze was found in the vehicle, she said they never bought any because they 'kept getting lost'.

Asked whether she had tried to smuggle the illegals into the UK to 'make some money' for the birth of her child, she replied: "I have never had any money. I always get by on what I can."

Her children will now be cared for by Bethel's sister.

Sophia Stapleton, defending, said while she was 'a party' in the people-smuggling enterprise, she did not have a prominent role.

"She was a passenger, she was heavily pregnant and would have been unable to move those tyres," she added.

Harris has been in custody since he pleaded guilty in January this year, having originally denied the offence.

He has eight previous convictions for 16 offences but nothing similar.

The maximum sentence for assisting unlawful immigrants is 14 years.

Judge Statman remarked that there was no humanitarian motive for the offence and accepted others higher up the chain were involved.

Passing sentence, he said although Bethel's children were an important mitigating factor, custody was inevitable for the deterrent message 'to hit home'.

"It goes without saying that assisting unlawful immigration into the UK is big business and the situation here is that this was a sophisticated enterprise," said the judge.

"You, Aaron Harris, were responsible for being a courier in an enterprise carried out for commercial gain and, to assist you in that enterprise, you Katy Bethel, knowing from start to finish what was going on, were in a way something of a decoy, because any customs officer looking into your van would have seen the fact that you were very heavily pregnant at the time.

"You were carrying an unborn child, one-year-old as I sentence you today. All four of them are under 10. I am very mindful indeed of the real concerns any judge will have in taking a mother away from a child of tender years.

"There is a compelling need for these children to be returned to the care of a mother and I weigh that heavily.

"But I regret to say that cannot lead me to suspend a prison sentence because it would ensure those at the top of the chain would inevitable turn to those who have this sort of family background, and pregnant mothers in particular, and use them so this evil activity of bringing people in from abroad will continue to take place.

"That is where the element of deterrence must hit home."

Assistant Director David Fairclough, from the Immigration Enforcement’s Criminal and Financial Investigation (CFI) team, said after the sentencing: "As these sentences demonstrate, abusing immigration laws and gambling with people’s safety are taken very seriously by the courts.

“Anyone thinking of doing the same should take this case as a warning. Working with our colleagues in Border Force we will catch you and ensure that justice is served.”