This is a very interesting question.
In his book ‘The Adventure of English’ Melvyn Bragg does an excellent job of showing the astonishing changes the language went through at this time.
Bear in mind of course that speaking ‘English’ in the 12th century was very, VERY far away from speaking English today. Modern English takes such a huge proportion of its vocabulary from French, that it is completely unrecognisable compared to the old pre-1066 language. As I understand it over 80% of the Anglo Saxon vocabulary has been lost, meaning it isn’t used anymore. The words that remain are often the common, ‘base’ type words to do with the connecting parts of a sentence, and to do with farming, the land, etc. All the ‘high’ status word for intellectual concepts are of French origin.
As I understand it, Henry V was the first to address the people in English, at least in written form. There is anecdotal evidence that some of the kings before that may have understood some English, but I think Henry V is the first where we have conclusive proof.
Starting in August 1417, Henry V promoted the use of the English language in government, and his reign marks the appearance of Chancery Standard English as well as the adoption of English as the language of record within Government. He was the first king to use English in his personal correspondence since the Norman conquest, which had occurred 350 years earlier.
Here's a sample text, in Old English, just to show the differences we are up against:
Cnut cyning gret his arcebiscopas and his leod-biscopas and Þurcyl eorl and ealle his eorlas and ealne his þeodscype, twelfhynde and twyhynde, gehadode and læwede, on Englalande freondlice. ¶
Cnut, king, greets his archbishops and his lede'(people's)'-bishops and Thorkell, earl, and all his earls and all his peopleship, greater (having a 1200 shilling weregild) and lesser (200 shilling weregild), hooded(ordained to priesthood) and lewd(lay), in England friendly.
And ic cyðe eow, þæt ic wylle beon hold hlaford and unswicende to godes gerihtum and to rihtre woroldlage.
And I kithe(make known/couth to) you, that I will be [a] hold(civilised) lord and unswiking(uncheating) to God's rights(laws) and to [the] rights(laws) worldly.
¶ Ic nam me to gemynde þa gewritu and þa word, þe se arcebiscop Lyfing me fram þam papan brohte of Rome, þæt ic scolde æghwær godes lof upp aræran and unriht alecgan and full frið wyrcean be ðære mihte, þe me god syllan wolde.
¶ I nam(took) me to mind the writs and the word that the Archbishop Lyfing me from the Pope brought of Rome, that I should ayewhere(everywhere) God's love(praise) uprear(promote), and unright(outlaw) lies, and full frith(peace) work(bring about) by the might that me God would(wished) [to] sell'(give).
¶ Nu ne wandode ic na minum sceattum, þa hwile þe eow unfrið on handa stod: nu ic mid godes fultume þæt totwæmde mid minum scattum.
¶ Now, ne went(withdrew/changed) I not my shot(financial contribution, cf. Norse cognate in scot-free) the while that you stood(endured) unfrith(turmoil) on-hand: now I, mid(with) God's support, that [unfrith] totwemed(separated/dispelled) mid(with) my shot(financial contribution).
Þa cydde man me, þæt us mara hearm to fundode, þonne us wel licode: and þa for ic me sylf mid þam mannum þe me mid foron into Denmearcon, þe eow mæst hearm of com: and þæt hæbbe mid godes fultume forene forfangen, þæt eow næfre heonon forð þanon nan unfrið to ne cymð, þa hwile þe ge me rihtlice healdað and min lif byð.
Tho(then) [a] man kithed(made known/couth to) me that us more harm had found(come upon) than us well liked(equalled): and tho(then) fore(travelled) I, meself, mid(with) those men that mid(with) me fore(travelled), into Denmark that [to] you most harm came of(from): and that[harm] have , mid(with) God's support, afore(previously) forefangen(forestalled) that to you never henceforth thence none unfrith(breach of peace) ne come the while that ye me rightly hold(behold as king) and my life beeth.
