The year is 50 AD and Julius Caesar is hungry for new conquests. At the helm of his triumphant legions, he decides to invade a small island at the very edge of the known world, a mysterious land named Britain.
Victory is swift and total... almost. A small village manages to resist, but it can't hold out for long, so the Briton Queen Cordelia sends her most faithful officer Anticlimax to seek aid in Gaul, in a small village known for its stubborn resistance to the Romans.
In this Gaul village, Asterix and Obelix already have their hands full, since their chief has entrusted them with the task of making a man of his good-for-nothing nephew Justforkix, freshly arrived from Lutetia - a task that is proving all but easy.
When Anticlimax arrives to ask for help, Asterix and Obelix are tasked with escorting him back to Britain with a barrel of their famous magic potion, with Justforkix in tow as the journey seems an excellent opportunity to educate the boy. However, nothing quite turns out as planned...