Trucks, buses and cars inched slowly past checkpoints at the English port of Dover and headed across the Channel on Thursday to the French port of Calais.
It came after France partially reopened its borders with Britain following a scare over a rapidly spreading new virus variant.
The travellers are being held up by the slow delivery of coronavirus tests which have been demanded by France following the news of the new variant.
Among the waiting vehicles were several coach loads of Romanian workers travelling home for Christmas.
Onboard were families and young children who had been on the coach for 5 days without proper food or showers.
The announcement of the coronavirus variant added to anxieties at a time when Europe has been hit by soaring new virus infections and deaths.
Europe as a whole has recorded over 500,000 virus-related deaths, according to a tally by Johns Hopkins University that experts agree is probably an undercount due to missed cases and other factors.