From French to Middle English

William the Conqueror and his nights brought the French language into England. The variety of French used is known as Anglo-Norman. English became a vernacular language, it lost all status. The Church continued to use Latin, the Court French. Written evidence has been found of that situation. English began to have loanwords which came from French. 

Costume, apparel and robe (Fr.)
Animals in the field kine, ox, swine (Eng) but on the table veal, mutton, pork (Fr.) 
The first sentence taught to us by Miss Shackleton was
'Six éléves chasses troi porcs au tour de mur.'
Six scholars chase three pigs round the wall.
Memory of a French lesson long ago.


1204 when King John lost all lands in France earning him the name 'Lackland'. English rose in importance and French diminished.

Fourteenth Century is acknowledged as the beginning of the Early Modern Period.

1385 Grammar schools in England adopted English and abandoned French tutelage. 

1399 Henry IV the first monarch since the Conquest to use English as his first language.

Middle English words can still be found in the dialects of today.

Middle English dialects
Old English  (Southern) West Saxon
South-Eastern (Kentish)
Old East Mercian (East Midland and West Midland)
Old English Northumbrian (Northern - North of the Humber)

In the 1300s, variety of speech/writing was the norm.

Trevisa’s 1385 translation of Higden, is evidence for the decline of French. It embellishes the original author’s remarks about northern dialects of English, as evident in this extract from the modernised version of his translation. Can you identify the different criteria that he uses in evaluating ‘the language of the Northumbrians’ here?

Criteria
Sharp / piercing / rasping sounds
Unshaped words
Unintelligible to Southerners

So, it seems in the 1300s the North-South Divide was much in evidence. Indeed the proximity of Northern England to Scotland (where dwelt 'aliens') is commented upon. The North / Northerners as uncouth.
Southern dialects were seen as almost the norm.

Standardisation - selection - codification - elaboration and implementation

Caxton's printing machine brought about a need for standardisation. 

From 1430 onwards government documents were written in English.

"The Parliamentary Archives hold millions of historical records relating to both Houses of Parliament dating from 1497."