How was England formed?

How was England formed?
The existence of England is one that is often taken for granted and looked at far too scarcely. This may be due to the overshadowing history of the development of Great Britain and the United Kingdom, but nonetheless, in order for these unions to be formed, England had to already exist - and it actually has since 927 AD. So, how was England created, who claimed the land before the English, and how did it become the nation that we know today?..