PROROGATION is a curious legacy of medieval parliamentary practice. Monarchs in the middle ages had the right to summon a great council of barons, bishops, knights and burgesses for the consideration of public affairs, and the right to prorogue – or interrupt – the sittings of this great council.

The British monarch who is best known for an attempt to use this power in person was Charles I. His impromptu prorogation of Parliament in 1628 precipitated a period of personal rule known as the Eleven Years’ Tyranny, which ultimately resulted in the Civil War and his own execution.

The Fixed-term Parliaments Act 2015 changed the previous conventional rules on dissolution, but not on prorogation. It remains a matter of royal prerogative, which by convention has since the development of parliamentary democracy been exercised on the advice of the Prime Minister.

Prorogation is a routine and uncontroversial mechanism used to formally end one session of Parliament so that a new session can be held.

A new session means a new Queen’s Speech and therefore an opportunity for the government both to set out its policy agenda and to prove that it enjoys the confidence of the House of Commons.

Since the Parliament Act requires a bill rejected by the House of Lords to be passed again in another session of Parliament, prorogation has been used on occasion to fast-track legislation through Parliament.

Prorogation also causes any bill currently going through Parliament to lapse, but since in normal circumstance the government has overall control of Parliament’s legislative timetable, this has not generally given rise to any problems – when prorogation occurs in a planned way, by a government enjoying the confidence of a majority in the House of Commons, it is usual for any uncontroversial legislation to be wrapped up, and to receive royal assent, before prorogation takes place.

Last week, the Queen made the necessary Order in Council to authorise the prorogation of Parliament. The new Prime Minister, having only faced Parliament for one day since his appointment, and with a shaky, disputed and unproven parliamentary majority, was keen to minimise the number of parliamentary days during which opposition to a No-Deal Brexit could effectively express itself, whether in the form of a vote of no confidence or an opposition-sponsored bill requiring the Prime Minister to seek another extension to the Brexit deadline.

This raised an interesting constitutional question: should the Queen have refused Johnson’s request to prorogue Parliament in such circumstances?

Despite the conventional rule that the Queen normally acts on Prime Ministerial advice, it is recognised that there are certain royal prerogatives that the Queen may exercise (or refuse to exercise) contrary to the advice of the Prime Minister.

These are the reserve powers of the Crown which by convention can – albeit only in rare and extraordinary cases – be deployed at the Queen’s personal discretion. For example, before the Fixed-term Parliaments Act, it was widely accepted that the Queen could refuse a requested dissolution of Parliament in certain circumstances in accordance with the so-called “Lascelles convention”.

A crucial element in the exercise of these reserve powers is the role of the Queen as a neutral and impartial guardian of parliamentary democracy.

The Prime Minister only attains the moral right to advise the Queen by virtue of the fact that he or she enjoys the confidence of a majority in the House of Commons.

If the Prime Minister does not enjoy the confidence of the House of Commons, then that authority is weakened. In particular, if a Prime Minister were to request a prorogation of Parliament in order to avoid holding and losing a vote of no confidence, it could be argued that the Queen has a conventional duty to refuse, at least until the House has met and has signalled that it does (or does not) have confidence in the Prime Minister.

To refuse prorogation under such circumstances would be a courageous move by the Queen, because this particular reserve power is – to be fair – not as clearly established by convention as some others.

Seen from the perspective of the overriding principle of parliamentary democracy, it would nevertheless be the proper one.

Charles I used the prerogative against Parliament. Elizabeth II has done likewise. By taking what seemed like the safer course, she has endangered parliamentary democracy – and with it damaged her own legitimacy.

This is not entirely the Queen’s fault – she would have benefited from clearer, more explicit constitutional rules. A republic would not fix this problem. Clarity about the constitutional rules would.

In particular, consideration should be given in any Scottish constitution to an explicit reserve power to refuse prorogation to a Prime Minister who does not have the unequivocal support of the Scottish Parliament.