What happens if Supreme Court rules Boris Johnson misled the Queen? Robert Peston asks

At the close of Supreme Court proceedings on Thursday, there was quite a lot of to and fro about what it would actually mean if the judges find the prime minister unlawfully misled the Queen when proroguing parliament.

Which was understandably interpreted by some knowledgeable observers as a signal that the judges may indeed find that Boris Johnson unlawfully prevented MPs from sitting at this critical time for the UK.

The big issue they have to decide is whether they have a locus at all, whether the PM’s use of the royal prerogative to send MPs home for five weeks is - in the jargon - justiciable, or an issue for any court.

Will a condemnation of the government come - and will it be charactarised as a success by the prime minister? Credit: PA

The consensus among lawyers is that those arguing for the prosecution, Pannick and O’Neill, had the best of this argument.

And if they did, lawyers tell me it is open and shut that the judges will take the further step of finding that Johnson exercised the royal prerogative for an improper purpose; namely to prevent MPs and Lords from exercising their most important duty and function, scrutinising the PM (the executive branch of government) and legislating.

What then?

Well, the government’s submission to the court was that even if the Supreme Court finds Johnson acted beyond the law nothing actually changes - because the action of proroguing parliament is parliamentary procedure over which, according to the Bill of Rights, the courts have no reach.

Which inevitably outrages the plaintiffs, Gina Miller, the SNP and Sir John Major.

But the plaintiffs do not appear to have a clear position about whether a finding against Johnson should mean that in practice the prorogation never actually happened and the house is in fact still sitting (against the evidence of our eyes) - or whether there would need to be a new order in the Privy Council to summon back MPs.

Gina Miller, who brought the case, leaves the Supreme Court. Credit: PA

It is all (you guessed) very messy and time consuming, with the clock ticking inexorably towards Brexit day on 31 October.

And whether the PM is losing sleep over any of this I rather doubt, since he is the 21st century populist version of the class traitor - namely a fully paid up member of the metropolitan elite who won’t weep when his outriders denigrate the judges as rich and privileged London Remainers hellbent on scuppering Brexit.

If the Johnson premiership stands for anything in its infancy it’s characterising every defeat and conventional humiliation as a victory.

And also perhaps pragmatism elevated to high art, since in a matter of weeks - as the SNPs Joanna Cherry said last night on my show - Johnson is expected to argue to the Supreme Court himself that when MPs legislated to force him to beg for a Brexit delay, rather than exit without a deal, it was they who broke the law.

Even for Johnson, judges have their uses.