You need to brush up on your history my friend. The number of times the island has changed hands runs counter to your point, and the current inhabitants certainly aren’t some continuation of an ancient people.

Rome held it, the Britons held it, the Picts invaded from Ireland, the Angles and Saxons had it after beating the Picts and killing the Britons…the list goes on. There isn’t some sacred ancient culture at stake and I’m sure the groups that were kicked out by the current inhabitants would take umbrage with your point if they could speak up.

I’m not even going to dive into “London is a miserable failure.” That’s just another hand wavy talking point. I’m not even sure by what metrics you’d measure how London is a “miserable failure.”