PARIS—Travellers about to board a train from Paris to London on the day quarantine rules in Britain were due to lapse were upset on Monday by a last-minute decision to keep them, calling it “ridiculous,” “cruel,” and “incoherent.” Anyone arriving from France will have to quarantine at home or in other accommodation for 5 to 10 days, the government said on Friday, even if they are fully vaccinated against COVID-19. The fact that England scrapped most coronavirus restrictions on Monday made it even more bitter for those about to check in on the Eurostar at Paris’ Gare du Nord station. “It’s incoherent and … frustrating,” said Vivien Saulais, a 30-year-old Frenchman on his way back to Britain, where he lives, after visiting his family. “I am forced to do a 10-day quarantine while the British government lifts all the restrictions and is going for a policy of herd immunity.” Britain …