I am delighted that the UK Supreme Court has followed the lead of Scotland’s Supreme Court and ruled that Boris Johnson’s shut down of parliament was unlawful. The effect of the ruling is that Parliament should never have been prorogued in the early hours of the morning of Tuesday 10 September. Therefore, parliament is technically still sitting, it could resume immediately and get on with the job of holding this minority Tory Government to account.

The Scottish constitutional tradition, dating back to the Declaration of Arbroath and the Claim of Right, is that neither the Monarch nor the Government is above the law. This is in line with the modern principles of Constitutional democracy and I am glad that the UK Supreme court agrees.

READ MORE: First Minister's full Sky News interview on Supreme Court ruling

Under English constitutional law, Parliament is supreme and throughout the Brexit referendum, the Leave side claimed to champion the sovereignty of the British Parliament. The decision of Boris Johnson to prorogue Parliament like this flies in the face of such claims and has further exposed the hypocrisy of the leave campaign.

Some will no doubt persist in the fallacy that by making this ruling the UK Supreme Court has strayed into the field of politics. In the Scottish court, Lord Drummond Young had the perfect riposte to this nonsense when he said: “The courts cannot subject the actings of the executive to political scrutiny, but they can and should ensure that the body charged with performing that task, Parliament, is able to do so.”

The UK Supreme Court has made the ruling necessary to restore democracy and the rule of law. Now politicians must make sure that ruling is respected.

While Parliament was suspended the Prime Minister went ahead with webcast videos under the title “The People’s PMQs” putting himself up for pre-selected and screened questions through social media rather than facing direct questioning in Parliament. He has sought to silence scrutiny by elected representatives in the chamber of the House of Commons, across select committees and all the other forms of scrutiny of the Westminster parliamentary system. He was, in effect, parodying, and so subverting, the true principle of his accountability to Parliament under Britain’s uncodified constitution.

READ MORE: Supreme Court: Boris Johnson acted unlawfully in suspending parliament

In the meantime, his government refused to obey the will of Parliament that the private messages of certain Government officials concerning the reasons for the prorogation be put in the public domain and sidestepped difficult questions over Operation Yellowhammer. Away from Brexit, Lis Truss broke the law on arms sales to Saudi Arabia without any consequences.

MPs must now return so we can scrutinise what this Government is up to and if necessary, hold the Prime Minister and his ministers in contempt of Parliament. I along with my colleagues across Parliament will be tabling Urgent Questions to try to force Ministers to come to the despatch box to answer.

Boris Johnson’s behaviour is wholly lacking in integrity. It is pretty clear he lied to MPs about the reasons for the prorogation and misled the Queen. He was forced to give documents to the Scottish court, which showed disdain for parliamentary democracy and a desire to lay a false trail as to the real reasons for the prorogation. No doubt that is why he refused to swear a written statement on oath in support of his position and why no other minister was prepared to do so either. It also explains the Government’s refusal to release the further documentation ordered by Parliament as it would probably give the game away completely.

The true dominant purpose of prorogation was, as Scotland’s Supreme Court judges correctly observed, to stymie Parliamentary scrutiny of the executive regarding Brexit In normal times any Prime Minister guilty of such conduct would have resigned immediately, but we are not in normal times. I suspect that he will keep going and it’s clear that he will consider trying to prorogue Parliament again. His behaviour is more like a dictator than the leader of a democracy.

This whole sorry mess has been a defining moment in the failure of the British state. Scotland deserves better than this and it is now clearer to more and more of our fellow citizens than ever that the only way to protect Scotland’s economic, social and cultural interests and our constitutional tradition is to become an independent state with a written constitution ensuring the sort of checks and balances that will prevent Executive abuse of power.