Before reading this discussion outline ask yourself: If the U.K. and Germany are the dominant two economic powerhouses within the EU, and the UK gives the EU system $500 million per week to share with the rest of the EU member nations (wealth spreading),…. what happens when the UK deposits stop, the member nations dependency remains, and Germany is the only powerhouse left trying maintain the system?
Standard and Poors (S&P) has downgraded the United Kingdom bond rating from AAA to AA as a punitive punishment for the Brexit vote.

NEW YORK, June 27 (Reuters) – Longer-dated U.S. Treasury yields fell to session lows on Monday after Standard & Poor’s lowered United Kingdom’s credit rating by two notches following its vote to depart from the European Union last Thursday. (link)

Punitive Punishment?  That’s exactly what this is.  This is a purely a political move by global bankers, institutional financial and political ideologues, within the financial markets.  The global cabal of elite financial interests are pissed; the peasants are revolting.

Bond rating agencies  like S&P and Moodys are financed/compensated by fees paid to them by the financial entitles they serve, the BIG CLUB. Period. Full Stop. End of sentence.
Think of an analogy:

If building inspectors were directly paid by builders, and builders were a consortium of protected political ideologues concerned about their own best interests (Big Club), how many building inspections would fail?  Then ask: whose building inspections would fail?  Insiders, or Outsiders?

Too cynical, you say – not even close.  This is an insiders game, a political insiders game.  The global financial market consists of a billionaires’ club with exclusive membership, and exclusive financial interests.   The market is completely rigged by ideologues who control the inputs and outputs.
To prove this point consider this article from “MARCH 2008” referencing the UK housing market, and S&P bond ratings, exactly five months before it completely collapsed:

(link)
In March of 2008 Standard and Poors said the UK “nonconforming (sub-prime) housing bonds were resistant to downgrades”  Yeah, you can consider that reference point a “MIC DROP” moment.
Here’s a more salty explanation:

George Carlin is right; and right now the “Big Club” is pissed off about Brexit !