Our coat of arms contains;

the red border signifying the Royal Command;

the green cross symbolizing true, peaceful Christianity;

the tablets of the Ten Commandments, representing God’s law;

the crown of a sovereign to uphold the law;

the symbol of the hand of living men, pledging allegiance to the barons’ committee as commanded in Article 61;

the Article 61 of the 1215 Magna Carta, bearing the Royal seal;

the multi-ethnic handshake showing that the Royal Command is to “all those of our land”, and that race makes no difference.

We were a group standing under constitutional law, and that our Cornation oath specified “God’s law”, and that the Bible used during the ceremony contains a New Testament.
I would like to add something.
An earlier codifecation of our law, the Doom book of Aelfred included a “Christian code of ethics”. Quote from Wikipedia:
[The Doom Book, Code of Alfred or Legal Code of Ælfred the Great was the code of laws (“dooms,” laws or judgments) compiled by Alfred the Great (c. 893 AD) from three prior Saxon codes, to which he prefixed the Ten Commandments of Moses and incorporated rules of life from the Mosaic Code and the Christian code of ethics.]
Wikipedia cites three prior Saxon codes, but much is made of the way in which Aelfred compiled and codefied “the best laws of the land”. The law was in the land before the Saxons came.
This is what “The law of the land” means.
The Saxons had been defeated, here because we were already a nation of great strength.
They were not defeated by occupying Romans, but by armies of the British people under British kings, at battles that are documented and have places named after them.
Even after the great massacre of 457 where the defeated Saxons treacherously killed most of the British leadership at a peace conference we still beat them.
It was in the reign of King Arthur 2 in the 6th century that a “comet” struck Britain causing catastrophe, and allowing the Saxons to invade and gain control.
(We were ruled from Wales by the way, but that is a digression).
History assures us that the Saxons kept our law, as did the Normans after them.
But if the Saxons just wanted to live here, then why all the fighting?
The answer is simple, and you have to pay attention here:
Christianity came here around  AD 35.
That pre-dates the Roman Catholic Church and the Council of Nicea. We were not slaves of such a political organization or believers of such fictionalized religion of standardization.
We were, specifically Gnostic Apostolic Christians.
The Saxons came seeking to impose the political control of the Church of Rome, which they finally did when we were not able to fight.
But that was not our religion.
They kept our law, they say, but they forcefully put us under Rome.
As I see it, Roman Catholicism is not the religion of the land, but Gnostic Apostolic Christianity is.
Therefore it is the principles and ethics of Gnostic Apostolic Christianity that the law of the land must conform to.
This is my opinion based on what I have learned, and if I had to specify therefore what the green cross relates to then that is what I would say, or more specifically I would say that the cross relates to the PRINCIPLES AND ETHICS OF Gnostic Apostolic Christianity AS THEY APPLY TO LAW.
And I think that anyone who would not agree with such principles and ethics as being suitable to guide law must be a thoroughly dispicable character in any case.
And btw, it seems that this issue, control of our land by Rome or not may be the most central issue in real fact.

You can hear what I’m talking about in this clip, very important obfuscated history:

It mentions the great massacre of 457 art 31:40 and the Christianity conflict at 37: 25