I know that on 15 October 1337 (Gregorian), English King Edward III officially laid claim to the kingship of France, effectively "declaring his independence" (an anachronistic phrase, I admit) and obviously refusing further homage or tribute to the French king. Was this vassalage to France the only time that the English monarch was forced to pay homage to a foreign power? If there were other times, when were they?
England came under the control of Sweyn Forkbeard, a Danish king, after an invasion in 1013, during which Æthelred the Unready abandoned the throne and went into exile in Normandy. Following the death of Sweyn Forkbeard, Æthelred the Unready returned from exile and was again proclaimed king.
Following the decisive Battle of Assandun on 18 October 1016, King Edmund, son of Æthelred the Unready, signed a treaty with King Cnut of Denmark, son of Sweyn, in which all of England except for Wessex (southwest England) would be controlled by Cnut. Upon Edmund's death on 30 November, Cnut ruled the whole kingdom as its sole king.
Cnut would be known as Cnut the Great and he ruled over the North Sea Empire
When the eleventh century began its fourth decade, Canute was, with the single exception of the Emperor, the most imposing ruler in Latin Christendom. . . . [H]e was lord of four important realms and the overlord of other kingdoms. Though technically Canute was counted among the kings, his position among his fellow-monarchs was truly imperial. Apparently he held in his hands the destinies of two great regions: the British Isles and the Scandinavian peninsulas. His fleet all but controlled two important seas, the North and the Baltic. He had built an Empire.
A point of note, the King of England in the time you mention (14th century and previous) was only a vassal of the King of France in so much as he held the French lands from the King, i.e. Normandy/Gascony/Aquitaine. The King of England, per se, was never a vassal of the French King.
That said, the Kingdom of England was previously tussled over by the Danish, as mentioned in another post, and lets not forget the Roman Empire which controlled Britain from the first century to the fifth.
