The British Constitution is a polite conversation.
There are tensions, but they are rarely articulated.
The parties know full well that confrontations are possible, but good sense and good manners will usually ensure that nothing becomes too embarrassing for anyone involved.
And so it is with the various "privileges" and analogous rights known to English law.
A privilege confers a right - often an absolute right or discretion - on those who wish to invoke its protection.
There are a number of such privileges in English law.
For example, there is "parliamentary privilege" which ensures that anything said in respect of parliamentary proceedings is free from any civil action or criminal law sanction.
There is also the universal jurisdiction of the High Court. There is no "order" which the High Court cannot make, even if it is futile and not capable of practical execution.
One of the most intriguing aspects of the Trafigura litigation was the possibility that a High Court injunction could be held to restrain parliamentary privilege: an unmoveable object and an irresistible force.
In the end, the apparent conflict was resolved, as it often is in domestic matters before the crisis comes to a head.
Today's evidence by James Murdoch at the select committee is suggestive of another such conflict.
He was relentless in blaming the external lawyers: the more he called them "distinguished external counsel" the more he dumped on them.
His lawyers cannot say anything back: News International have "legal professional privilege" which prevents disclosure of their legal advice. There will be confidentiality obligations too.
But what if the House of Commons were to summon the external lawyers and ask them to give evidence?
It may be that the lawyers could not be compelled to provide evidence on pain of "contempt of Parliament".
However, if they chose to give evidence that would surely be free of any threat of civil suit.
Parliamentary privilege would trump legal professional privilege and confidentiality. (Though there may be professional code aspects not rebutted by Parliamentary privilege.)
It would be a fascinating prospect, not least for constitutional law geeks.
A staple of story telling since early human history is to pit two absolute powers against each other. The tradition continues in superhero comics and fantasy films.
There is always drama in the clashes of titans.
The skill of the storyteller is not just to posit such a match, but to engross the listener or reader in how the contradiction is resolved.
Could "parliamentary privilege" be used to defeat "legal professional privilege"?
Or would the latter prevail?
One does not know what would happen when such privileges collide.