PREFACE
Mostly it is difficult to tell the startpoint when a language is born. However, in the case of English, we can say with absolute certainty, that there was no English language in Britain preceeding the invasions of the Germanic tribes in 4th, 5th and 6th centuries.

CLASSIFICATION
The English language belongs to the Germanic branch of the Indo-European language family, and thus is related to Balto-Slavic, Italic, Greek, Albanian, Indo-Iranian, Celtic and other Indo-European language groups.

GERMANIC PROTO-LANGUAGE
The first Germanic language, Proto-Germanic, dates at the latter half of the 1st millenniun B.C. and it is generally agreed that its urheimat was in the present-day Scandinavia, particularly southern Sweden and Denmark. The ancestors of Germanic peoples settled in the area some time around 2500 B.C. The differentiation of Proto-Germanic from the other Indo-European dialects/languages began in the 6th century, by so-called Grimm's law, also known as the Germanic consonantal shift. I am not going to discuss it in detail here since this essay is about English language.

FROM COMMON GERMANIC TO ANGLO-SAXON
The first migration of Germanic tribes out of their urheimat took place in the 8th century B.C., but in greater number occurred first in the latter half of the 1st millennium B.C. At this time the Common Germanic language dissolved into three separate groups - the western/Ingvaeonic group, the northern/Istvaeonic group (speakers of the Proto-Norse language) and the eastern/Irminonic group (ancestoral to Gothic, Burgundic, Longobardic, Vandalic and others). In the first half of the 1st millenniun, the Ingvaeonic group dissolved into several languages, most notably Old Frankish, Old Saxon, Old High German and Old Frisian. Two of them, Old Saxon and Old Frisian went on to have a great influence on the future English language. As the Saxons, Angles and Jutes invaded Britain, they pushed the Celtic tribes northwards and westwards and thus reduced the influence of Celtic languages on the English language. Roughly from this time on, we can already speak of the Anglo-Saxon language, by some recognised as the Old English, the earliest stage of the English language.

ANGLO-SAXON/OLD ENGLISH
The Old English language would resemble modern High German or Icelandic languages and these three share many similarities in the structure as well. It was referred to as 'Englisc' by its native speakers.

The pronunciation of Old English was closer to the continental Germanic languages than to modern English, for instance the voiceless velar fricative /x/ was widely present (today vanished in many Germanic languages, remains in High German, Dutch, Icelandic and some Frisian varieties, as well as some English varieties...the consonant in Slovak 'chata') and the voiceless palatal fricative /ç/ (very common in modern Germanic languages...the consonant found in High German 'ich'). The vowels were much closer to modern German or Swedish as well.
It pertained the classical Germanic case system - nominative, genitive, dative, accusative and unlike modern English, had clearly distiguishable subjuntive mood.

VIKING RAIDS AND DANELAW
In 793 a viking took place in the monstery of Lindisfarne and in the 8th and 9th centuries, Danish raiders kept the English busy fighting for their lives and territory. This had a great influence on the English language, since many Old Norse words entered the language - notably the pronoun 'they'. Another example the the verb 'call', which had pre-Norman form of 'ceallian' (pronounced tche-ah-lee-an) but was replaced by Old Norse 'kalla'. Therefore we don't say 'chall' but 'call' today.