What language did King John speak?

English

Answer:

King John of England (1166-1216) had lands in both England and France. He would have spoken both French and English to his subjects. At that time the nobles of England all spoke French (not English) and the English language was just starting to take shape. As an educated man whe would have been trained in Latin (the language of the Magna Carta which he signed) and Greek.

As an Example of King Johns English look at Chaucer's Canterbury Tales to see how much the language has changed.

Example of Chaucer's and King John's English from Canterbury Tales

WHEN that Aprilis, with his showers swoot

The drought of March hath pierced to the root,

And bathed every vein in such licour,

Of which virtue engender'd is the flower;

When Zephyrus eke with his swoote breath

Inspired hath in every Holt and heath

The tender croppes and the younge sun

Hath in the Ram his halfe course y-run,

And smalle fowles make melody,

That sleepen all the night with open eye,

(So pricketh them nature in their corages; , inclinations

Then longe folk to go on pilgrimages,

And palmers for to seeke strange strands,

To ferne hallows couth in sundry lands;

And specially, from every shire's end

Of Engleland, to Canterbury they wend,

The holy blissful Martyr for to seek,

That them hath holpen, when that they were sick.