I was going to say that i sincerely hope british police judges and prisons are strictily subject to the rule of law. Not any "practical" agreement needed from them. Otherwise we are speaking of factual powers, honor tribunals and general lynching, all left well behind in any civilized country, but FP was much faster.
About Queen agreement, it is real queen agreement or only formal symbolic agreement?
It is mostly symbolic, but there are a number of stories:
(a) Queen Victoria refused to sign an Act prohibiting lesbianism
(supposedly because she refused to believe that it existed,
but possibly to protect her not so hetero-sexual relatives)
(b) Queen Elizabeth II refused Margaret Hilda Thatcher's request
to dissolve Parliament immediately after the recapture
of The Falkland Islands.
Police regularly use their discretion as to when to enforce
laws and when not to. Otherwise most of us would be in court.
The UK government decided to impose a non discretionary charge
upon defendants for all contested criminal convictions of nearly £1,000.
This resulted in various magistrate stating that this meant that victims
did not get compensation and the innocent were pleading guilty.
When the government dug in many of those magistrates resigned at
which point the government backed off because it needed magistrates.
The current arrangements within the umbrella of the EU court are not satisfactory.
(1) For instance the Australian Julian Paul Assange is effectively imprisoned in
the Ecuadorian embassy in London because he is afraid to go to Sweden and risk
being extradited to USA and maybe water boarded under a President Donald Trump.
(2) Thirty party rights laws that the UK and EU have gone along with mean that
one can buy a product, and then people one has never heard of sue you for all that
you have via front companies that conceal their identity behind limited liability walls.
There is a genuine debate as to whether the UK should have a structured written
constitution, a supreme court like the USA or a new UK Human Rights Act; but
that is all a poor excuse for hiding in the imaginary protection of the EU.