The London dialect was a slightly modified version of the east Midland dialect; it was the east Midland dialect with a perceptible southern bias.
It was that form of the east Midland dialect which was more tolerant of other dialects and permitted greater flexibility. The three important factors which gave the London dialect a high degree of acceptability all over England were the following: (i) Being the dialect of the capital, it had a large number of expected advantages over the other dialects. As London was the centre of the political, economic, commercial, judicial and cultural network of the whole country, people in different dialect areas of England had to communicate with the speakers of this dialect. Acquiring a working knowledge of the London dialect was therefore a practical necessity for a large number of people in different regions of England. (ii) Chaucer, perhaps the greatest English poet before Shakespeare, was a Londoner.
He was born in London; he spent most of his time in London and died in his own house in London. Although he used a large number of French words in his writings, his writings are all in the London dialect. With his poetic genius he added a great deal of creative vitality to this dialect and because of him this dialect acquired the status of a first rate literary medium. (iii) When Caxton started the first printing press in London in 1476, he wanted the books to be printed by him to conform to the norms of the London dialect. By printing books in this dialect, he gave this dialect a certain degree of fixity and stability and also a kind of respectability that the other dialects of England lacked. Because of these advantages the London dialect was, towards the end of the Middle English period, recognized all over England as the most efficient and the most widely intelligible of all the dialects of Middle English.
It is no surprise, therefore, that later it transcended the localized image of a dialect and established itself as a standard medium for literary writings. The following advice given by Puttenham to his contemporary poets can be quoted in support of the inference that by the sixteenth century the London dialect had acquired the image of being the only regional variety of English which poets could use as the medium of their literary writings. Ye shall therefore take the usuall speech of the Court, and that of London and the shires lying about London within six miles, and not much above.