In recent years, the authorities have cracked down on people attempting to stowaway or hide under lorries travelling through the Channel Tunnel, the preferred method for migrants to reach the UK.
The French and British governments installed walls, high-wire fences, extra security and cameras, as well as more on board checks, such as carbon dioxide monitors to detect stowaways, on haulage vehicles to shut off access to this route.
The carbon monitors can detect people breathing within a 40ft range, and can be calibrated to ensure false alarms from fruit and vegetables are not triggered.
The normal atmospheric level of CO2 is 400 parts per million, but the presence of one individual breathing can increase that to 500 parts per million when standing in an empty shipping container. The average person can exhale as much as 24 litres of CO2 every hour.
Even when there is a slight draft, the new detectors are able to confirm a person’s presence within a couple of hours.
More lorries are also subjected to random spot checks, when they are taken through scanners that can detect people hiding within shipments.
Drivers were also threatened with huge fines if they are caught with migrant stowaways within their consignments.