Even without customs procedures, small hitches can cause chaos at Dover and the authorities are forced to “stack” lorries on approach roads

It is a “high-risk”, six-year project that is already behind schedule and if it fails to arrive on time ports will grind to a halt and gaps will appear on supermarket shelves. Not surprisingly, traders and hauliers are starting to get worried.

A new computerised customs system to replace a creaking 25-year-old platform was supposed to be switched on for testing last month, before a full switchover in October. Instead, the £71 million project is expected to be completed in January 2019, weeks before Britain looks likely to quit the European Union.

“The worst-case scenario is that everything grinds to a halt,” Duncan Buchanan, deputy policy manager of the Road Haulage Association, said. “There’s very real concern among our members about what might happen if