Many have to wait for several hours, as all international arrivals and passport controls have to be handled manually.
The British Home Office announces that the problems are being dealt with.
“We are working to resolve the issues as soon as possible and are liaising with ports and airports to minimize disruption to travellers,” it said.
Monday is a “bank holiday” in Great Britain, a holiday where most of the country’s residents are allowed to be off, which is said to mean increased travel.