A range of the U.K.'s top lawyers have spoken out following the Supreme Court's historic ruling that the Prime Minister's decision to prorogue parliament for five weeks was unlawful.

Mishcon de Reya and Blackstone Chambers won out in the case, representing businesswoman Gina Miller. Mishcon dispute resolution partners Rob Murray and James Libson instructed Blackstone Chambers' Lord Pannick QC and Tom Hickman QC.

Pannick argued that Boris Johnson's decision to prorogue parliament was an "unlawful abuse of power".

Sir John Major, supported by Herbert Smith Freehills partner Andrew Lidbetter, also intervened in the case. Blackstone's James Eadie QC and Landmark Chambers' David Blundell were acting for the government.

Dan Tech, head of public law at CMS, called the ruling a "remarkable assertion of judicial authority", adding: "The readiness of the court to overturn such a highly political prerogative power is what makes this decision legally so notable."

Lidbetter of HSF said: "This is plainly a case of fundamental constitutional importance in relation to the relationship between parliament, the executive and the courts.

"We are pleased that the Supreme Court has found that the decision to advise Her Majesty to prorogue parliament was unlawful, because it had the effect of frustrating or preventing the ability of parliament to carry out its constitutional functions without reasonable justification.

"When reaching its conclusions, the court specifically referred to the unchallenged evidence of Sir John regarding the usual time it takes to draft a Queen's Speech."

Prime Minister Boris Johnson is now expected to face requests to bring members of parliament (MPs) back into their role in parliament.

Ros Kellaway, partner and head of the competition, EU and trade group at Eversheds Sutherland, reacted in a statement: "This is an extraordinarily strong, and most importantly unanimous, judgment from the full Supreme Court. There is no wiggle room for the government here. Furthermore, the court has dealt immediately with the effect of its judgment on the unlawful prorogation, [so] parliament can start sitting immediately."

Jim Cormack QC, litigation partner at Pinsent Masons, added that by focusing on the effects of prorogation, "the Supreme Court has restricted the Prime Minister making it very difficult for him to attempt to prorogue again in the run-up to the Brexit deadline".

He went on: "In the eyes of the courts, he could very well be seen to be acting unlawfully on a second occasion by interfering with parliamentary scrutiny without a clear justification during an unprecedented and critical period for the future of the UK."

But whether the government tries to prorogue again and whether MPs agree to a recess for party conferences will depend on how much time is left for parliament to scrutinise the government's policy on Brexit, according to Andrew Hood, regulatory partner at Fieldfisher.

In any case, Charles Brasted, public law partner at Hogan Lovells, pointed out that if Mr Johnson sought to prorogue parliament again in the near future, "he would have to give cogent and lawful reasons for doing so, and it is highly unlikely that it could be of anything like the length previously intended", adding: "The law has now returned this matter firmly into the court of politics."

Mishcon de Reya's Libson was upbeat, saying: "We are glad that the court recognised the threat to the rule of law caused by a prorogation based on misleading advice given to the Queen.

"This second success for our client Gina Miller in the Supreme Court is a testament to her resolve to take whatever steps are required to ensure executive overreach does not become a feature of our democracy.

"This case shows that our courts can be relied on to hold the executive to account when necessary and is evidence of the robustness of our system of separations of powers."

But not everyone was happy about the ruling. One Magic Circle firm corporate partner said: "My first reaction was depression. It feels to me that we're going down the same route as the U.S., with the courts getting involved in politics. No matter your views on the topic, it is a worrying trend.

"I'm sure there will be a massive crowd calling for him to resign and it puts the government in an extremely difficult position. Does he now command confidence of her Majesty if the courts ruled this way?

"I've had more discussions in the last few weeks about Brexit than in the last three years. It's absolutely front and centre now. Previously there were too many moving parts to predict. There are questions still over what this means for dealflow, and which regulators are going to be able to approve things."

Other partners pointed out the probable effect on the Brexit timeline, with Sally Shorthose, an IP partner at Bird & Bird, asking: "Where does that leave Brexit?  With parliament taking a consistently anti-no-deal Brexit stance, an October 31 exit no seems less likely unless the government can pull a rabbit out of a hat in the form of an agreement with the EU that will be acceptable to a majority of parliament."