Modern English derives from Old English, the language spoken by the Anglo-Saxons who settled in Britain in the 400s. This was a complex language related to modern Dutch, German and the Scandinavian languages.
Under the influence of Old Norse, spoken by the Vikings, and later of French, brought in by the Normans, many foreign words were adopted and the grammar became simpler.
The language used between the 1100s and early 1500s is known as Middle English. Different dialects were spoken in different parts of the country. In the late 1300s the poet Geoffrey Chaucer wrote in the dialect spoken in London, which rapidly became the standard English dialect.