Asterix in Britain (1986) on Netflix

Plot summary

Caesar has conquered Britain, but one village of Britons refuses to submit. Its people expect to fall soon, so a villager crosses to Gaul and asks his cousin Asterix for some of the magic potion that keeps the Gauls ahead of Rome. The druid Getafix gives him a barrel, and the chief Vitalstatistix orders Asterix and Obelix to carry it across the sea, with Dogmatix. On the crossing they rescue a Phoenician trader from pirates, and the trader gives Asterix a bag of herbs as thanks. A Roman officer on the galley learns of the errand and takes word to the Roman commander in Londinium.