I'm curious about this too. I just read a book about William Marshall called The Greatest Knight and the author made the argument that it was in the early 1200s that this idea of Englishness began b/c John had lost the Avengin's French possessions and so everyone wasn't hoping back and forth across the channel all the time, French language started to take a back seat at court, the Magna Carta was signed and the specific rights of an English noble were recognized and this concept of a specific English identity began to take shape. I was wondering how accepted this view is?

I want to answer this, but you will have to excuse my answer being a little short because I am on mobile.

I feel that it is also relevant for this question that the word 'English' had barely started to be used before the Normans arrived. In the Anglo Saxon period, the people of what we call England were initially divided into a number of smaller kingdoms, which gradually coalesced into one. The key turning point was the Viking invasion of the ninth century, which meant that Wessex became the only independent kingdom in Britain under Germanic rule. As the Vikings were pushed back, Wessex and it's rulers maintained their superiority, and this became the origin of a single kingdom of the English.

There are a number of reasons why it is difficult to track down the beginnings of these people calling themselves English. It is, for example, difficult to say why they chose to be English rather then Saxon, since many continental sources for the period, including Gregory of Tours, refer to them as 'saxones'. The choice of English seems to come from it's adoption to describe the members of the English church, as used in Bede's ecclesiastical history. Specifically, many Latin texts with an identifiable connection to Bede or the archbishopric of Canterbury seem to have used the word 'angli' to describe the Germanic people if Britain from as early as the seventh century, while still individually referring to them as groups of angles, Saxons and Jutes, according to which Kingdom they belonged to. There was a separate identity depending on whether you were talking about the single English church or the separate identities of the kingdoms (this reflects the multi-faceted nature of identity in medieval cultures).

The adoption of the word Angli and its old English equivalent Angelcynn or Angletheode to describe the Anglo Saxon rulers can be traced through it's adoption in royal titles. King Alfred, touted by Victorian historians as the first king of England and a great national hero, was never more than 'king of the angles and Saxons'. His successor, Edgar, is in many ways seen as the most successful Anglo Saxon king, and in some charters was referred to as king of the Angli, yet the Anglo Saxon Chronicle, on his death, refers to him only as a king of the angles and a friend of Wessex. It is clear that even by 975, less than 100 years before the arrival of the Normans, English identity barely existed for anyone.

Historians of medieval England rarely look back before 1066, and in the case of this question, I feel that since the idea of English identity was so new at the time of the arrival of the Normans, this may be relevant to a discussion of why they failed to adopt it for so long. By the Norman invasion England was a single political entity which had been referred to as such for barely a century, and for a large portion of that time it had even ruled by a Danish king who had imposed his own supporters as 'earls' to rule over the aristocracy, most of them Danes themselves. It is hardly surprising that the Norman aristocracy saw England more as a territory for conquering than a ready formed nation that they were becoming part of.