A lot of the ideologues in the Civil War (especially the radicals, the left-wingers, the Levellers and the Diggers) were teeming with ideas as they attempted to overthrow the monarchy. They were all harking back to these historical models that they'd read in their history books.
They knew what they thought about early English history, and they believed that the English had lost their liberties in 1066. They believed the story of the Norman Yoke was good history. This comes through very clearly in the writings of great Levellers such as Gerard Winstanley.
'They were all harking back to these historical models that they'd read in their history books.'
'England, you know, hath been conquered and enslaved divers times, and the best laws that England hath (viz Magna Charta) were got by our forefathers' importunate petitioning unto the kings, that still were their task-masters; and yet these best laws are yokes and manacles, tying one sort of people to be slaves to another...
'The last enslaving yoke that England groaned under (and yet is not freed from) was the Norman, as you know; and since William the Conqueror came in, about 600 years ago, all the kings did confirm the old laws, or else make new ones, to uphold that Norman Conquest over us; and the most favouring laws that we have doth still bind the hands of the enslaved English from enjoying the freedom of their creation.
'You of the gentry, as well as we of the commonalty, all groaned under the burden of the bad government and burdening laws under the late King Charles, who was the last successor of William the Conqueror: you and we cried for a Parliament, and a Parliament was called, and wars, you know, presently begun, between the King, that represented William the Conqueror, and the body of the English people that were enslaved ...
'... and William the Conqueror's successor, which was Charles (I), was cast out; and thereby we have recovered ourselves from under that Norman Yoke.'
An Appeal to the House of Commons (1649)