The ruling of Scotland’s highest court that Boris Johnson’s suspension of parliament was unlawful since it aimed to “stymie” it — and that he in effect misled the Queen — is extremely grave. It is not, to be sure, the final word. The three judges applied Scots law, which can diverge on constitutional matters from its English counterpart. The High Court in London found differently. The UK’s Supreme Court must now issue a definitive opinion. Yet whatever that court decides, the Scottish ruling strengthens the impression of a government ready to trample on centuries-old conventions. It is yet another self-inflicted blow for a hapless British prime minister.

As the Financial Times argued at the outset, proroguing parliament for five weeks in the midst of political turmoil and just seven weeks before a potential no-deal Brexit was an affront to democracy. The government continues to argue otherwise, speciously claiming that suspension is normal and necessary to prepare for the launch of a new parliament session and legislative agenda. The argument that the prorogation extends only slightly parliament’s customary September break for party conferences is equally insulting.

Prorogation before a Queen’s Speech usually lasts only a few days. Normal business such as select committees — and hence scrutiny of the executive — continues during the conference recess, but not when parliament is suspended. As one of the Scottish judges concluded, “the circumstances, particularly the length of the prorogation, showed that the purpose was to prevent?.?.?.?scrutiny” of the government.