What happens next after the Supreme Court ruled that Boris Johnson unlawfully prorogued parliament?

The prime minister is facing a tough few days as MPs and peers return to Westminster earlier than expected

The Supreme Court's stunning ruling that Boris Johnson unlawfully closed Parliament earlier this month has sent shock waves through Westminster.

MPs and peers, who were not due back in Parliament until mid-October, are instead returning tomorrow. The prime minister is cutting short his trip to New York. The last day of Labour's annual conference has become a sideshow, with Jeremy Corbyn's big speech hastily moved forward.

But as chaos reigns, what is likely to happen next?

The only certainty is that the House of Commons and House of Lords will both sit on Wednesday. That was confirmed by the speakers of both houses within hours of the Supreme Court verdict being delivered.

It is less clear what comes next, but we have a good idea of what will happen.

Johnson, forced to return earlier than planned from his trip to the United Nations, will be expected to deliver a statement in the House of Commons and take questions from the very MPs he thought he sent packing until next month. It is not likely to be an easy ride.

The government is also expected to table a motion proposing an immediate parliamentary recess to enable Tory MPs to attend the Conservative Party conference next week, as would normally be the case.

But with the opposition parties likely to oppose the move, the vote will rest on whether the 20 or so MPs kicked out of the Conservative Party by Johnson earlier this month decide to back the government or not. The conference is expected to go ahead regardless, but it would be a very different occasion if MPs and cabinet ministers have to be in Westminster.

Johnson responded to the Supreme Court verdict by reiterating his demand for a general election, and the government is likely to hold another Commons vote in the coming days to try to trigger an early poll.

It also remains to be seen whether the prime minister will attempt to prorogue parliament again - this time for a shorter period - as he, his ministers and government lawyers have all suggested he could.

In the meantime, the government could call debates and votes on the bills that had to be dropped because of the prorogation but will be restored now that the suspension has been declared null and void.

Opposition MPs are also plotting how to make the best use of their unexpected return to parliament. On Wednesday, they are likely to table a series of Urgent Questions on a range of issues, not least on the government's legal advice on proroguing parliament, which claimed that the suspension was lawful. The government will be asked to explain why its advice was so different to the view taken by all 11 of the Supreme Court judges who heard the case.

The Liberal Democrats are expected to table a series of Urgent Questions on events that have taken place in the two weeks since parliament was prorogued. These are likely to include the collapse of Thomas Cook, and the government's forced apology for breaking rules on the sale of arms to Saudi Arabia.

With no agenda in place for the days that follow, MPs are likely to propose a series of emergency debates, held under Standing Order 24 of the Commons rules. It would be for John Bercow, the Commons speaker, to decide which of these to grant.

MPs are also mulling whether to force a vote on finding the government in contempt of parliament over its refusal to publish a series of documents that the Commons demanded earlier this month. Ministers have refused to publish their full set of impact assessments on a no-deal Brexit, and correspondence between advisers relating to the decision to prorogue parliament.

One outstanding question is whether Jeremy Corbyn will use Johnson's mauling by the Supreme Court to call a vote of no confidence in the government. A prime minister being found to have unlawfully closed parliament is unprecedented, and many will argue that it warrants a vote to oust him.

However, with many of the former Tory rebels having said they would not currently vote to topple the government, Labour is expected to wait until it has a greater chance of winning the vote, and until a no-deal Brexit has definitely been definitely.

Some opposition parties are suggesting going even further. Plaid Cymru has proposed that the archaic device of impeachment could be used to hold Johnson to account and remove him from office.

That is unlikely to happen, but at this stage anything is possible. With parliament back in the driving seat and the government having lost its majority, there is bumpy road ahead for the prime minister.