The highest court in the UK has ruled that the Prime Minister broke the law, with the effect of frustrating parliament and preventing MPs from debating Brexit. Politically as well a legally, it is a judgement that is unprecedented in modern British democracy.
It sets up a people-versus-parliament election campaign that Downing Street has been seeking, but under circumstances which it can't possible have predicted or desired.
Johnson is now facing calls for his immediate resignation - he dismissed those on the eve of the court ruling with a blithe “donnez-moi un break” while answering questions from journalists at the UN General Assembly in New York.
But Lady Hale’s words will follow the Prime Minister and the Conservatives throughout a snap election campaign that now looks more likely than ever, not just because of the Supreme Court ruling, but because of Labour’s own difficulties over Brexit at its party conference in Brighton.
It’s important to state that the ruling did not address the question of what the government’s intentions were in proroguing parliament - only their effect. The Supreme Court did not rule on whether Johnson ‘lied to the Queen’.
That won’t make much difference to the opposition attack lines in the election campaign to come, perhaps as early as November. It is even harder today to see a scenario where the country doesn’t go to the polls before the end of 2019.
In practical terms, it is now up to the Commons Speaker John Bercow and his counterpart in the Lords to decide when parliament reconvenes. They may decide that with the Prime Minister in New York and the Labour conference not set to end until Wednesday afternoon, MPs should only return on Thursday.
Whenever they do, an emergency debate is certain to follow. Labour could also decide to press a vote of no-confidence in Johnson’s government. Whatever happens next, there is no script: this is truly a one off.