Johnson explained why in a letter to colleagues. To introduce a "new bold and ambitious domestic legislative agenda for the renewal of our country after Brexit" he needed a new Queen's Speech (which begins a new session and sets out that agenda), which meant Parliament must first be prorogued.

The length of the prorogation - 33 days - was highly unusual. Since 1930 the average prorogation has lasted for five calendar days.

To many, the timing and length of the prorogation made it pretty obvious this was an attempt to limit the ability of Parliament to interfere with Brexit, deal or no-deal, ahead of its October 31 deadline.

The prorogation more than halved the number of pre-Brexit days when government ministers could be held to account; there would be no select committees asking awkward questions or asking for sensitive documents, no urgent questions in the House, no emergency debates.

Former prime minister John Major gave evidence in court that there was "no practical reason" why the government needed a five-week break between Parliament's sessions apart from the "obvious political interest that the Prime Minister has in there being no activity in Parliament".

It's a rare, but not unheard-of tactic. In 1948 the British government prorogued Parliament to get around House of Lords opposition to a new law. In 2008 the Canadian prime minister prorogued the Canadian Parliament to delay a vote of no confidence.

So the government's Leader in the House of Commons went up to Balmoral. Reportedly, Jacob Rees-Mogg simply read out the prorogation order, and the Queen said "approved". Though prorogation is an exercise of the Queen's powers, she performs it automatically when advised to by the government.

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We know from court documents that Downing Street had planned the prorogation since mid-August. They arranged a phone call between the Prime Minister and Queen the day before Rees-Mogg's visit to advise her to approve it.

That conversation remains confidential. What explanation Johnson gave for requesting the order, or whether he gave any at all, we cannot say.

But if he gave his public explanation, which seems most likely, then three senior Scottish judges have called it untrue.

Earlier this week the Scottish Court of Session ruled that the advice (that is, the instruction) to the Queen to prorogue Parliament was unlawful - a decision to be appealed next week in the Supreme Court.

Lord President of the Court of Session, Lord Carloway, in his reasons, found: "the true reason for the prorogation is to reduce the time available for Parliamentary scrutiny of Brexit … in the context of an anticipated no deal Brexit".

Lord Carloway remarked about the absence of any affidavit to the contrary from the government - indeed all three judges remarked that, in court, the government had provided no direct evidence on its reasons for prorogation.

Lord Brodie - another judge on the Scottish Court of Session - agreed: the prorogation was "blatantly designed to frustrate Parliament at such a critical juncture in the history of the United Kingdom".

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So, we have one court saying Johnson lied - at least to the public, and possibly also to the Queen.

But it wasn't the lie itself that made the prorogation unlawful. He could have told the Queen any reason for prorogation, true or false, and it would still have been unlawful because of his underlying motivation.

And the two other courts said it neither matters if Johnson lied, nor what his motivations for prorogation were. The Queen had to do what the Prime Minister told her to do, whatever his reasons. And because it was a fundamentally political decision, he was allowed to tell her to do it.

All these decisions have been appealed.

Next week the Supreme Court will have the ultimate voice: does it matter if a Prime Minister lies to his Queen, or to the public? And if it does matter: did he?