Shame on me? 
I explained it succinctly
Succinct means brief and clear. You explained nothing.
By the way, I notice others here have since provided all the data points you could easily have googled for yourself.
Oh, so it is the Magna Carta you worship after all. But which Magna Carta? The one the king signed under duress in 1215 and promptly renounced? The 1216 version? The 1217 version? The 1225 version? The 1297 version? Medieval England went through Great Charters like modern Thailand goes through constitutions (to say nothing of the not-so-great charters).
True, common law was influenced by these charters, and common law is not worthelss, but the concept of liberty (oops, freedom) existed long before the Anglo-Saxons were a thing, and the concept of divine right – usually considered the antithesis of the “freedom” expressed in the Charters – existed long after them (and still does), at least in England.
In the hilarious “entrapment” video that Jotham so kindly showed us, Maggie also lists equity as evidence of the greatness of (as she says) the British. Okay.
But apart from so-called Parliamentary supremacy and the legal system (as if civil law were utter tyranny), the only other evidence of this greatness she can come up with is that Britain has not been “occupied” in the last 1000 years.
I’m sorry, what’s that you were saying about water?
Strangely, Maggie doesn’t mention the mass deportation of a well known immigrant community with ties to the Middle East 
nor the reversal of that policy a few centuries later. 
I wonder, which one of those makes better evidence of Anglo-Saxon supremacy in the fields of freedom, pragmatism and anti-stupidity? 
And no, the wetness of water is not a theory.
How about the whiteness of polar bears? 