As the March Brexit deadline looms, the Eurotunnel teams at both ends of the channel tunnel are on a mission to keep everything moving: getting dog owners home after Crufts, keeping trucks moving despite strikes at French customs, and making sure the trains keep circulating, no matter what, on the world’s busiest and biggest trainset.

With up to 400 trains a day running on its 62 miles of track, the channel tunnel is the busiest railway system in the world. And doing things at the double is key to its success. Two countries built it. There are two terminals. And there is duplication at both ends.

Eurotunnel teams have a quarter of a century’s worth of experience in getting cars and lorries onto trains. It all hinges on a finely tuned system using letters to send the right vehicles to right trains. But when pre-Brexit passport checks cause slow coaches, how will the allocation team in Folkestone keep the endless stream of half-term holiday traffic flowing?

After 25 years in business, Eurotunnel is at a junction, with many of its staff facing retirement and new recruits being drafted in. And the next batch of wannabe shuttle drivers has just arrived for the first round of testing. The tests, however, are ruthless, with a 90% fail rate, so who will make it through?