An HGV driver has said he was "shocked but not surprised" at the discovery of a lorry in Essex containing 39 dead bodies.
Driver Jim* said those in the haulage community had become adept at knowing what vehicles were carrying at ports, and claimed human traffickers were "fairly easy to spot".
"If I'm sitting in my lorry in the middle of Calais I can watch lorries coming by, and I can point out that that one is smuggling beer, that one is smuggling wine... everybody knows," he told talkRADIO.
"The people who smuggle people, they are fairly easy to spot. I'm just very surprised this hasn't happened before."
Jim explained that he was suspicious of lorries that "hold back" at ports.
"They sit back and watch and see how many people have been put under the scanner, how many people have been brought in to be detained or looked at... and once they know the coast is clear, that the customs officers are busy, then they go into the port," he recounted.
"People can say to us 'Why do you not tell the authorities?'. I do know of people that have sent anonymous letters to the authorities with names, addresses and phone numbers, and they still see the people going about having a nice life."
Police have confirmed that the people discovered in the back of the refrigerated lorry yesterday were all Chinese nationals.
It is believed the vehicle had travelled from the Belgian village of Zeebrugge.
"A driver, nine times out of 10, will know on the paperwork what is meant to be in the lorry. That does not meant to say that that is what is in it," Jim continued.
"If the lorry has been sealed by customs and you have papers for the load, and customs have seen and inspected the load and sealed it, then you can guarantee that is what's in it.
"But people get their own seals and put them on the back of a trailer and say yes, that's a sealed trailer, and use that as an excuse to get away."
*Name changed for anonymity