Doggerland

Long ago, The peninsula Doggerland connected Britain to mainland Europe. Later on the peninsula sunk completely. But what if a part of it survived, as an island, and later was influenced by the Celts, Romans, and Germanic people. And later became a powerful kingdom in it's own right? In this timeline Doggerland, (which is called Septria from the roman word Septendrionalis, meaning "north") is, in modern time, a member of NATO, the UN, and the EU. It is a constitutional monarchy in the Scandinavian style with a king as head of state, and a Prime Minister as head of government. It's official language is Septrian, an Anglo-Frisian language.