The Supreme Court has ruled that the prorogation of Parliament was unlawful, in a historic decision for British politics.

The Supreme Court began by unanimously agreeing to overturn an earlier ruling by the English High Court that prorogation was not justiciable. This meant that the Supreme Court determined it was able to rule on the legality of Parliament’s suspension.

Having decided the matter was justiciable, the Supreme Court went on to rule that the five week suspension was indeed unlawful, in what will be seen as a significant blow to Boris Johnson. Senior Judge Lady Hale said that the “prorogation was void and of no effect”, also stating that both the House of Commons and House of Lords, “can take immediate steps to enable each house to meet as soon as possible.

The decision is unprecedented, and troubling for the Prime Minister. For the Supreme Court to find that Boris Johnson acted unlawfully in shutting down Parliament during a moment of national crisis could have significant implications for the PM.

Of particular pain was a sentence regarding the Queen, which said that “It is impossible for us to conclude on the evidence… that there was any reason – let alone a good reason – to advise Her Majesty to prorogue Parliament for five weeks.” Any suggestion of misleading the Queen will be extremely damaging to the PM, and some opposition MPs have already called for his resignation.

In response, the Speaker of the House John Bercow said that “the House of Commons must now convene without delay.” The next steps remain to be seen however; the ruling is a first, and the procedure is now in new political territory. The Labour party are also in the middle of their party conference, with Jeremy Corbyn responding the news while on stage. The Prime Minister is in New York today attending a General Assembly of the United Nations, leaving him unable to return and deal with today's decision.

The recalling of Parliament will be painful for the Prime Minister, and is added to a growing list of defeats since he took the premiership. His majority in the Commons is gone, and his reputation as someone who can get things done has taken a significant beating since MPs reconvened after summer.

It should be noted however that bringing Parliament back does not equate to the end of Brexit. MPs still have just over a month to try and come to a resolution, or convince the EU to agree to an extension. It does mean that Boris Johnson could face much more scrutiny over his Brexit plans in the next few weeks. There is a chance however that the PM could prorogue Parliament again; though likely for a shorter period considering today’s ruling.

The pound has seen volatility following the announcement; increasing at first, before subsiding slightly as traders wondered about what could happen next. Downing Street have responded only to say they are “processing” the judgement, and this week could still see a lot of political drama.