One main aspect of Lucas North's character I do not completely understand, is the concept why he has the tattoo "The Ancient of Days" on his body.
The blog article at Spooks Fan Blog (link here) shows the ambivalence of this figure for William Blake. This in my opinion is the central point in understanding its relevance for Lucas North.
Lucas North does not, as I once saw mentioned, see his fate in the hands of G-d and the tattoo refers to the inability to build ones own fate.
But what I see as central in his interpretation is his fighting against such rules and rules of any kind.
Therefore, he is not a defender of state, country, religion or any system defending those systems, like the MI-5. Lucas, as a result, is in constant inner turmoil with his own position in the secret service, defending systems he does not believe in.
Perhaps that is one of the reasons, why his believe in Harry Pearce to help him at the end is no real alternative for him. MI-5 is no alternative or safe haven for him.
So he tries to fight on his own and looses.
William Blake - The Ancient of Days
for Lucas North as for William Blake is not, as he would be for freemasons, the creative power who created the visible world with all its measurable rules and the ordering entity of the world and the whole universe.
For both I suspect, it is a symbol for a builder of dubious systems which do not hold happiness for the individual or mankind in general.
Lucas North broke because of his fight against systems, rules and social order as we know it. What goals he as a young man John Bateman wanted to achieve, is left open.
This dissatisfaction with current establishment made him vulnerable for Vaughans ideas and manipulations. But why John Bateman and later Lucas North did not more actively persue his own ideas and try to realise them, still remains a mystery to me. Strong believers like Lucas North normally try to follow their 'right path' without looking sideways.
(I will come back again to William Blake and "The Ancient of Days", as the topic fascinates me greatly, also its similarity to aspects of freemasonry. I am awaiting a book on the topic, where I hope to get more information about the believe system of William Blake. I will keep you informed.)