Mo Robinson had picked the trailer from Purfleet, Essex, after it arrived from Zeebrugge, Belgium at 12.30am today, police confirmed.
Cops said the cab and trailer were then attached and driven away from the port at around 1.05am.
CCTV shows the lorry making its final journey packed with the dead suspected migrants – including one teenager – 30 minutes before the grim discovery was made.
Mo Robinson can’t be seen in the video but the red and white Scovia lorry is left-hand drive.
His family, from County Armagh, told Belfast Telegraph they hadn’t “heard from him” and “don’t know what is going on”.
It was originally believed the lorry entered the UK via a ferry crossing from Dublin to Holyhead, Wales, on Saturday.
But police have now confirmed it was only the lorry’s cab that travelled from Holyhead on Saturday.
Meanwhile the trailer – with the 39 bodies – travelled 173 miles from Zeebrugge in Belgium to Purfleet, Essex.
It was then unloaded from the ferry in Purfleet at 12.30am today, and attached to Robinson’s lorry.
Both lorry and trailer then left the port at 1.05am. Less than 35 minutes later ambulance and police made the grim discovery of the 39 bodies in the back.
Cops said tonight the lorry was being moved from the industrial estate to a “secure location” at Tilbury Docks to recover the bodies.
Police tonight bowed their heads as the lorry containing the bodies of the 39 dead migrants was driven away.
Meanwhile, in a separate incident, nine suspected migrants have been rescued from the back of a truck on the M20 in Kent travelling towards London.
The incident happened between Junction 9 near Ashford and Junction 8 near Maidstone.
Robinson’s social media is awash with pictures of what appears to be the same cab as the lorry involved in the horror.
It has an identical “The Ultimate Dream” decal on the windscreen – with Mo Robinson branding it “The Polar Express” on his social media.
The driver has also used the hashtag “irishfridgemen” and “cowboy club” while posting about the lorry on Instagram.
He has been a HGV driver for more than five years.
Mo Robinson doesn’t own the lorry, which was registered in Bulgaria in 2017 by an Irish company. It has not returned to Bulgaria since then.
Robinson appears to make regular trips to Denmark and Sweden, which would mean driving through Britain.
A 25-year-old former schoolmate of the arrested lorry driver told Sun Online: “When I found out who it was I really could not believe it. No way that is true.
“I went to Portadown College with him. He was in my year for two years. Everybody that has ever met him has only positive things to say.
“He is a really chilled, good, decent guy. all the people he is friends with are from a really nice group. He is just a normal, decent guy. You can’t imagine anyone saying anything bad about him.”
Tonight, police investigating the deaths raided a home in County Armagh.
The 39 people who died have not yet been identified by police.
Deputy Chief Constable Pippa Mills, of Essex Police, said: “In order to maintain the dignity of the people who have sadly lost their lives, we will be moving the lorry and trailer shortly.
“Once that movement has happened we will remain here to complete some scene examinations before we can allow all the business operators back to their premises.
“The lorry and the trailer will he moved to a secure location at Tilbury Docks so the bodies can be recovered whilst preserving the dignity of the victims.
“We are yet to identify them and must manage this sensitively with their families.”
Haulage experts said the group who died had “little or no chance of survival”.
Even if the trailer was not chilled the victims may have suffered agonising deaths as oxygen slowly ran out.
Last night sources close to Irish police said the lorry’s refrigeration unit was turned on.
They said the container was normally used to transport biscuits.
The lorry had been captured on Automatic Number Plate Recognition 25 times in recent weeks between Dublin and Holyhead.
Forklift dealer Andy Larkin, who works on the Essex industrial estate where the lorry was found, says he spotted the cab parked in a similar spot just 12 hours before the bodies were found.
He said: “I walked down that way around 2pm on Tuesday and spotted it. It stood out because it had lots of chrome work on the cab, it looked American, a custom job.
“The curtains in the cab were shut so maybe the driver was having a kip when I was walking past.
“I also noticed it because it was parked outside an old warehouse.
“It used to be a refrigerated warehouse but it’s been shut for a few months.”
Experts say the container appears to be refrigerated – meaning temperatures can reach as low as -25C causing people to “lose their lives pretty quickly”.
It is not yet known how the victims died or if the refrigerator was switched on.
Road Haulage Association chief executive Richard Burnett said the “horrific conditions” would be “absolutely horrendous” in the dark lorry.
He added: “This tragedy highlights the danger of migrant gangs people-smuggling on lorries.
“It’s highly unlikely that if this vehicle has come from Europe that it’s been physically checked.”
Police have now removed the lorry from the industrial estate after forensic officers combed it for clues.
DUP councillor Paul Berry told MailOnline this evening that dad-to-be Robinson’s family were “distraught”.
Mr Berry said: “I’ve spoken to the family a couple of times,’ he said. ‘At this stage they haven’t been informed of anything and the police don’t have to in these circumstances.
“Obviously they are very distraught. His mother is incredibly as well as his partner. They are just waiting for news. People keep ringing them up and asking ‘is it true?’ but they just don’t know.
“They contacted police themselves but a sergeant said he couldn’t tell them anything. It does seem unfair. The family at least should know that he has been arrested.”
Today’s horrific incident is the biggest disaster of its kind since 2000, when 58 Chinese stowaways died in a lorry travelling by ferry from Belgium to Britain.
Police are now working to the identify the 38 adults and one teenager but say it will be a “lengthy process”.
They were alerted by paramedics but it is not clear who made the original discovery. All 39 people were dead before the emergency services arrived.
Chief Superintendent Andrew Mariner said: “This is a tragic incident where a large number of people have lost their lives. Our enquiries are ongoing to establish what has happened.”
Boris Johnson said during PMQs that the perpetrators “should be hunted down and brought to justice”.
‘THEY SHOULD BE HUNTED DOWN’
The National Crime Agency confirmed they are assisting Essex Police and Immigration Enforcement to “urgently identify any organised crime groups” who may be involved.
A cordon is in place at Waterglade Industrial Park, which is currently closed.
It is also a mile from Intu Lakeside shopping centre and the M25 Dartford Crossing.
In 2000, 58 dead bodies were found in a lorry at Dover, after travelling from Belgium.
They were immigrants and likely died of asphyxiation after being trapped in the container for more than 18 hours.