Boris Johnson could be arrested by the end of the week.

What are the possibilities of a UK Prime Minister being arrested and possibly jailed for  Contempt of Court?


The Huffington Post tells us that

Judges are set to decide whether the unsigned letter sent by Boris Johnson asking for a Brexit extension from the EU complied with the Benn Act, or if the prime minister is in contempt of court.
Although Johnson sent a letter to the EU requesting an extension, as required by the so-called Benn Act, he did not sign it and also sent a second letter – which he signed – that said a delay would be a mistake.

At first Primme Minister Johnson was behaving childishly and it was the Westminster Parliament he was treating with contempt 

However

A hearing at the Court of Session in Edinburgh by Scotland’s most senior judge Lord Carloway, and two other judges, was postponed until after the deadline for the extension letter to be sent under the terms of the Benn Act.


Now that the deadline has passed, the hearing is set to resume on Monday but the prime minister’s attempts to avoid requesting an extension raises questions about whether the court views the unsigned letter – and second contradictory letter – as obeying the law.
The petitioners behind the legal challenge at the Court of Session, led by Good Law Project founder Jolyon Maugham QC, confirmed that the resumed hearing would go ahead on Monday.

During the case’s first hearing on October 9, the government’s lawyers assured the court that Johnson would adhere to the law in writing and before the judges – despite the prime minister’s repeated public declarations that he would never request an extension.
If the three judges find Johnson has failed to uphold the law, they could find him in contempt, with potential punishments including a fine or even a jail sentence.

Clearly the court accepted  the government's promise, to obey the law and by not signing the letter could indeed be found not to have deliberately misled the judges and had no intention of complying with any palimentry vote to seek a extention in writing.

EU Commission president Donald Tusk confirmed at 10pm on Saturday that he had received the prime minister’s request, tweeting: “The extension request has just arrived. I will now start consulting EU leaders on how to react.”
In his signed letter, Johnson wrote: “A further extension would damage the interests of the UK and our EU partners, and the relationship between us.”
The letter, to Tusk and copied to European Council president Jean-Claude Juncker, references his regret at being defeated over the Letwin amendment in the House of Commons on Saturday.
It states: “Regrettably, parliament missed the opportunity to inject momentum into the ratification process for the new Withdrawal Agreement.”
MPs voted by 322 to 306 in favour of amending the Brexit deal in order to withhold the Commons’ approval until the necessary UK legislation to leave the EU has been passed. The government’s response was to cancel Saturday’s vote on the deal, with it expected to be brought back before MPs during the week.
Joanna Cherry QC, an SNP MP who has been involved in bringing proceedings to court, described Johnson’s actions as a “childish trick of not signing the letter and sending a contradictory covering letter”.
She added: “Our legal team are instructed to remind the court that as well as promising to comply with the letter of the Benn Act, the PM also promised not to seek to frustrate the purpose of the legislation.
“It will be for the court to decide whether his actions in failing to sign the letter of request and sending a letter setting out his contrary intentions

I find it extraordinary that this is not the major news issue   in that  a UK  Prime minister faces arrest  for  contempt .

Plaid's Liz Saville Roberts Plaid Cymru MP Liz Saville-Roberts has previously  asked Speaker John Bercow for advice on whether they can table a motion to impeach the Prime Minister.

It might well be something that she should revive.