The continuous history of England begins in 455 AD, when the first of the English kingdoms was founded. The history of English as a written language, and of English law, begin in about 600 AD. The English language and English legal system have gone on to have a worldwide impact.
Of course the histories of the other nations of the United Kingdom are worth studying. But I don't know enough to do them justice, so I'll leave them for people who are more expert in those areas than I am.