On 23 May 2025, the Court of Appeal held that the Conservative Party was not exercising a ‘public function’ for the purposes of s 6 of the Human Rights Act 1998 when it elected Liz Truss as party leader, who would go on to be appointed as the Prime Minister: R (Tortoise Media Ltd) v Conservative and Unionist Party [2025] EWCA Civ 673. While this judgment has been described as ‘orthodox’ by Lewis Graham in the Administrative Court Blog, a broader question was left open by the Court about whether the ‘advice’ of an outgoing Prime Minister to the Sovereign as to who should be invited to become Prime Minister and form a government is justiciable.

In opining on that issue but not ultimately expressing a view, Singh LJ (writing for the unanimous Court) made some provocative statements about the constitutional conventions governing the appointment of the Prime Minister. Lord Justice Singh stated that it is ‘well-established by constitutional convention that the Sovereign will appoint the Prime Minister on the advice of the incumbent Prime Minister’ (at [36]). He effectively repeated this by saying that it is a ‘constitutional convention … that the Sovereign will follow the advice of the Prime Minister on the issue of who should be invited to form the next government’ (at [34]). And that when Prime Minister Boris Johnson was giving advice to the late Queen about who his successor should be, he was ‘acting as her principal adviser, in other words in his capacity as the then Prime Minister’ (at [34]).

This article seeks to explore the accuracy of these assertions. The better view is that the appointment of the Prime Minister is a reserve power, which the Sovereign can make contrary to the views or recommendation of an outgoing Prime Minister. I conclude with some remarks about how this affects the justiciability question.

Tortoises, Tories and Truss

In July 2022, Johnson resigned as leader of the Conservative and Unionist Party (Conservative Party), which triggered a leadership election within his party. He remained Prime Minister whilst the party conducted an internal process under its constitution (described as ‘stage 1’ by Singh LJ) to hold a ballot, which resulted in Liz Truss becoming party leader. After the results were announced in September 2022, Johnson informed the late Queen Elizabeth II that he would be resigning as Prime Minister and advised her to invite Truss to become his successor (this advice is ‘stage 2’). After Johnson’s resignation took effect, Her Late Majesty appointed Truss as Prime Minister (the appointment being ‘stage 3’).

Tortoise Media Ltd sought information about the membership of the Conservative Party that voted on the party leader in 2022. Tortoise Media argued that Art 10 of the ECHR imposed a positive obligation to provide information to the media but this argument could only succeed if the Party was exercising a ‘public function’. The media company maintained that, in conducting its leadership election, the Conservative Party was exercising a ‘public function’ because the winner of that election would, by constitutional convention, become the Prime Minister. That argument was rejected by Fordham J in the High Court and by Sir Geoffrey Vos MR, Singh and Dingemans LJJ in the Court of Appeal.

During argument in the Court of Appeal, counsel for Tortoise argued that Johnson was acting as the ‘delegate’ of the Conservative Party in stage 2 (at [34]). This was rejected by Singh LJ, who said that the advice was given by Johnson in his capacity as ‘the then Prime Minister’, who is the Sovereign’s ‘principal adviser’ (at [34]). Counsel for the Conservative Party argued that the appointment of the Prime Minister is a ‘personal prerogative power’ that is ‘exercisable in the sole discretion of the monarch and without the previous advice of a Minister’ (at [36]). Lord Justice Singh said that ‘this does not assist the Conservative Party in the present case because it is well-established by constitutional convention that the Sovereign will appoint the Prime Minister on the advice of the incumbent Prime Minister’ (at [36], emphasis added).

Is the Sovereign bound to follow the advice of the outgoing Prime Minister on their successor?

Although not without doubt, there is a great deal of scholarly literature that points to the view that the appointment of the Prime Minister, as opposed to other ministers, is a reserve power that can be exercised by the Sovereign without or contrary to advice. This makes it rather surprising to read the assertion that it is ‘well-established by constitutional convention’ that ‘the Sovereign will follow the advice of the [departing] Prime Minister’ (at [34], [36]).

For instance, Sir Ivor Jennings, in his book Cabinet Government, said that the Sovereign ‘need not accept advice as to the appointment of a Prime Minister’ (at 394). Peter Hennesy, in his book about post-WWII Prime Ministers, distilled the personal prerogatives of the monarch and noted that ‘[n]ormally an outgoing Prime Minister is asked to advise the Monarch on the succession’ and ‘if given, it is informal advice which can be rejected, rather than formal advice which must be acted upon’ (at 34).

Anne Twomey, in her seminal book on reserve powers, stated that the Sovereign ‘has no “adviser” when it comes to the appointment of the chief minister’ and therefore ‘there is no question of rejecting formal advice’ (at 116). Rodney Brazier, in his book Constitutional Practice, stated that it can be a ‘comfortable notion’ for the public if the Sovereign is acting on the advice of the outgoing Prime Minister but such advice is not constitutionally binding ‘ministerial advice’ (at 17, 40). Rather, it is merely the informed opinion of the political situation that a departing Prime Minister can bring.

A potential counterargument may draw on the work of Robert Hazell et al in Making Minority Government Work. They state, as one of the ‘lessons for Westminster’, that the Prime Minister ‘must advise the [Sovereign] who is likely to command the confidence of the House of Commons’ (at 68 [6.1.1]). The Prime Minister can ‘informally’ inform the Sovereign’s Private Secretary about political negotiations but should tender ‘formal advice on whom to invite to form a government’ once ‘it is clear who can command the confidence of the House of Commons’ (ibid). This is because the ‘golden rule is not to draw the Monarch into controversy or political negotiations’ (ibid). But Hazell et al stopped short of saying that the Sovereign is then bound to act on that advice. There may be a duty on the Prime Minister to assist the Sovereign in good faith and set aside party interest, but that is a different thing altogether to the Sovereign being required to follow any advice — even if ‘formal’ — from a departing Prime Minister on this issue.

As a matter of first principles, the principle of responsible government establishes two conventions relevant here. The primary convention is that the Sovereign appoints as Prime Minister the person who holds, or is most likely to hold, the confidence of the House of Commons. The second convention is that the Sovereign must exercise their powers on the advice of their responsible ministers. However, where a Prime Minister has been defeated in an election or lost a confidence vote in Parliament, they are no longer responsible to Parliament for the advice that they give. And even where a Prime Minister resigns as party leader but continues to hold confidence in the Commons, their advice about their successor (even if given before their resignation takes effect) is not conventionally binding advice because they would no longer be responsible for it to Parliament once their resignation took effect. Thus, the second convention is not enlivened on this very issue. Instead, it is the primary convention that controls.

Practically, if the Sovereign could only appoint the next Prime Minister on the advice of the outgoing Prime Minister, this would create problems if the latter died or was incapacitated and thus could not advise. There is also a risk that a departing Prime Minister may tender partisan or arbitrary advice that conflicts with the primary convention, or refuse to advise completely, leaving the Sovereign with no advice at all. It would be inconceivable that the Sovereign would act on advice to appoint a person that contradicts the primary convention.

Vernon Bogdanor, in his book explaining the aftermath of the 2010 election when no political party achieved a majority in the House of Commons in their own right, rejected the view that the outgoing Prime Minister is under an obligation to formally advise the Sovereign as to whom to appoint as his or her successor (at 22). He worried that, if the outgoing Prime Minister could tender binding advice, they could ‘make a mischievous recommendation’. Bogdanor posits, ‘Gordon Brown could have recommended David Davis, a Conservative opponent of [David] Cameron’s, for the succession’ (at 16).

Eugene Forsey, writing about constitutional conventions in Britain and Canada, stated that ‘it remains true that a retiring Prime Minister has no right to name his successor’: at 20. Like Bogdanor, Forsey was concerned about the potential for an outgoing Prime Minister to abuse this power including the ‘preposterous’ consequences if a ‘defeated Liberal Prime Minister should be able to advise the Governor-General to send for some Conservative other than the leader of the victorious Conservative party’ (at 20).

Ben Pimlott’s biography on Queen Elizabeth II describes three instances of historical practice that support the views taken in the academic commentary. First, when Prime Minister Winston Churchill resigned in 1955, he did not recommend a successor to the late Queen. Churchill said to his Principal Private Secretary, Jack Colville, that ‘[o]nce the Prime Minister resigns he can’t advise’ (Pimlott at 232). Churchill described the suggestion that an outgoing Prime Minister can advise the Sovereign to send for someone as their successor as ‘rubbish’. The Queen appointed Sir Anthony Eden as Prime Minister.

Secondly, when Eden resigned as Prime Minister, he ‘unequivocally recommend[ed]’ Rab Butler to the Queen as his successor (Pimlott at 259). The Queen did not accept this recommendation immediately. Instead, she consulted other elder statesmen of the Conservative Party, including Lord Salisbury and Churchill. Despite Eden’s recommendation, the Queen appointed Harold Macmillan as Prime Minister on the basis that he was more likely to enjoy the support of the various sections of the Conservative Party.

Thirdly, when Macmillan resigned as Prime Minister, he gave informal advice that the Queen should appoint Sir Alec Douglas-Home. The Queen agreed to do so but her Private Secretary, Sir Michael Adeane, stressed to her that as Macmillan’s advice was ‘non-constitutional’ she was not obliged to act upon it (Pimlott at 331).

Those three examples were made before the Conservative Party had adopted the current system of party members electing their leader. But the appointments of Eden and Macmillan confirm that the Sovereign acted without advice and contrary to the views of the outgoing Prime Minister. And the appointment of Douglas-Home shows that, even where the Sovereign agrees with the view of the outgoing Prime Minister, that view was considered informal and not binding. At the very least, Adeane’s intervention shows that any convention that departing Prime Ministers can give binding advice is seriously disputed.

The notion that the Sovereign is not bound to follow the advice of an outgoing Prime Minister on their successor continued after the major parties had adopted leadership elections. A close analogy to the Johnson-Truss change in leadership for a party with a majority in the House of Commons occurred in 1976. Prime Minister Harold Wilson resigned as Labour leader but, like Johnson, continued as Prime Minister until a new leader was chosen by the party. After James Callaghan won a ballot with Labour MPs, Wilson visited the Palace and informed the late Queen of the outcome of the party vote but left the appointment to her discretion. Wilson explained in his memoir (at 239):

Contrary to the views of some text-book writers, a retiring Prime Minister does not advise the Queen who should be sent for, still less is there any truth in one proclaimed view that if the Queen asks for his advice she must accept it. This was never so.

In reaching the opposite view, Singh LJ in Tortoise Media (at [13], [15] and [16]) appears to have relied heavily on the Cabinet Manual, which was first published in 2011. The Cabinet Manual points to examples of Prime Ministers not resigning until ‘there was a situation in which clear advice could be given to the Sovereign on who should be asked to form a government’ and leaves open whether these examples may ‘be regarded in future as having established a constitutional convention’ (at [2.10]).

This reliance appears to be misplaced. The Cabinet Manual was suggesting the possibility of a constitutional convention being developed ‘in [the] future’, not describing one that necessarily existed at the time of publication. The House of Commons’ Political and Constitutional Reform Committee found in a report published in 2011-12 that the ‘established convention’ is that ‘the Monarch is not obliged to take the advice of the outgoing Prime Minister, and may take advice from other sources’ (at [28]). And whether such a convention has solidified is open to serious doubt. David Torrance, in a Commons Library Briefing in 2024, stated that ‘the outgoing premier is occasionally consulted, but his or her advice is not considered binding’ (at 37 [4.1]). Similarly, a Lords Library Briefing in 2019 by Emily Haves stated that ‘the appointment of a prime minister is a reserve power, because the out-going prime minister could not be held accountable to Parliament for any advice he or she gave on this matter’ (at 3 [3]). It seems that any new convention has not fully solidified, let alone become ‘well-established’.

The attempt in the Cabinet Manual to provide for a clear choice to be offered to the Sovereign and thereby insulate them from political controversy is an admirable one. But Twomey warns that any attempt at creating a new convention that the Sovereign should or must act on an outgoing Prime Minister’s advice ‘potentially places the Sovereign in an invidious constitutional position’ (at 125). It has the potential to place the Sovereign in ‘even greater political controversy’ if the outgoing Prime Minister ‘gives mischievous advice or is ill-informed as to negotiations between and within the Opposition parties’ (ibid).

In conclusion, it is doubtful that there is a ‘well-established’ constitutional convention that the Sovereign appoints a Prime Minister on the advice of the outgoing officeholder. The academic commentary, first principles and historical practice point towards any ‘advice’ of an outgoing Prime Minister on their successor not being constitutionally binding.

Is ‘advice’ or recommendation from an outgoing Prime Minister justiciable?

It is understandable why any challenge to the appointment of the Prime Minister will focus on ‘advice’ rather than the appointment by the Sovereign. The position remains that ‘judges cannot enforce the law against the Crown as Monarch because the Crown as Monarch can do no wrong’: M v Home Office [1994] 1 AC 377 at 395. But ‘[t]he fact that the Sovereign could do no wrong did not mean that a servant of the Crown could do no wrong’ (at 408). Judicial review can be brought against ministers for the advice they tender to the Sovereign. That is what occurred in R (Miller) v Prime Minister [2020] AC 373 (Miller 2), which concerned advice given by Johnson to the late Queen to prorogue Parliament during the Brexit controversy. In that case, the Queen acted on the advice of Johnson and ‘[i]t is not suggested … that Her Majesty was other than obliged by constitutional convention to accept that advice’ (at [30]). The existence of this convention meant that, once the Court found the advice to be unlawful, the Order-in-Council made by the Queen and the actual prorogation were unlawful too (at [69]).

But, unlike the ‘capital “A”’ advice in Miller 2, the ‘lowercase “a”’ advice to the Sovereign about their next appointment for Prime Minister is not constitutionally binding. The chain from advice to action is broken by the fact that the Sovereign has a personal discretion, albeit constrained by the primary convention, in appointing the Prime Minister. As the late Queen’s decision to appoint Eden shows, this includes acting contrary to any recommendation by the outgoing Prime Minister. This makes Miller 2 distinguishable.

Suppose for the sake of argument that the advice from an outgoing Prime Minister is constitutionally binding. What then?

For starters, the ‘appointment of ministers’ appears in Lord Roskill’s list of examples of prerogative powers that are not amenable to judicial review in Council of Civil Service Unions v Minister for the Civil Service [1985] AC 374 (GCHQ case) at 418A–C. The issue, however, is not so clear. Lord Justice Singh notes in Tortoise Media that that list is dicta and some of the examples, including the prerogative of mercy, have been held in subsequent cases to be justiciable: at [37]–[38]. But despite these subsequent developments, the GCHQ case remains authoritative for the proposition that justiciability turns on the ‘nature and subject matter’ of the power. Decisions about who the House of Commons has confidence in at any point in time is an inherently political issue with strong party-political undertones. It can depend on party loyalties, political deals and intra-party leadership rules — these are not matters that are within the institutional expertise of the courts to speculate on.

Miller 2 emphasises that a relevant factor in determining justiciability is the presence or absence of meaningful political accountability. A prorogation, especially one with immediate effect, prevents ministerial accountability. Parliament is powerless to stop the executive act once it has begun. ‘[T]he most that Parliament could do would amount to closing the stable door after the horse had bolted’ (at [33]). It is this aspect that distinguishes a prorogation from a dissolution, which also appears in Lord Roskill’s list. A dissolution, which is followed by a general election, precipitates democratic accountability whilst a prorogation does not (Miller 2 at [4]). Like a dissolution, the appointment of a Prime Minister invites parliamentary accountability.  There is a plethora of ways by which confidence in the Prime Minister can be tested in the House of Commons, including through votes on the ‘humble Address’ on the King’s or Queen’s Speech, a supply bill, a motion of no confidence or some other motion or bill designated as ‘a matter of confidence’. As Fordham J described in the High Court, the ‘safeguarding remedy’ against a Prime Minister without the confidence of the Commons ‘lies squarely within Parliamentary accountability and scrutiny’ (at [47]). This is a ‘constitutionally suitable and appropriate safeguard’ that ‘render[s] judicial review inapt and unnecessary’ (ibid). So even if the Prime Minister could give binding constitutional advice on their successor to the Sovereign, the best place to correct any mistake is Parliament, not the courts.

Conclusion

The Court of Appeal in Tortoise Media was able to dispose of the proceedings by deciding that the Conservative Party’s internal leadership election conducted under the party’s constitution was not a ‘public function’. There was never a realistic chance that Johnson’s advice to the late Queen would be the subject of judicial review in that case because Tortoise Media did not in fact challenge the advice given at stage 2.

What appears troubling is the assertion that there is a constitutional convention that the Sovereign will follow the advice of the outgoing Prime Minister on who their successor should be. These obiter remarks in Tortoise Media should be treated with caution. The Court of Appeal acknowledges that the issue was not fully argued before it (at [38]). If the issue arises again, counsel should draw attention to the large body of academic commentary and historical examples supporting the view that the Sovereign is not bound to follow such advice. In appointing the Prime Minister, the Sovereign focuses on who can command majority support in the House of Commons. Whilst the views of an outgoing Prime Minister — someone who is a seasoned political operator — can be insightful, the King or Queen can decide the issue for themselves without or against that view.

But if the departing Prime Minister can give binding advice on their successor, I argue that the advice is not justiciable because the best place to correct wrong advice is Parliament itself. For this power, Parliament is the best place to ensure that the primary convention is upheld.

When courts are faced with issues about political conventions, they should heed the wise words of Lord Neuberger PSC in R (Miller) v Secretary of State for Exiting the European Union [2018] AC 61 that judges are ‘neither parents nor the guardians of political conventions; they are merely observers’ (at [146]). Importantly, ‘they can recognise the operation of a political convention in the context of deciding a legal question … but they cannot give legal rulings on its operation or scope, because those matters are determined within the political world’.

Dane Luo is the Farthing Scholar in Administrative Law at Pembroke College, University of Oxford

(Suggested citation: D. Luo, ‘There is ‘Advice’ and then there is ‘advice’: The Constitutional Conventions on the Appointment of the Prime Minister’, U.K. Const. L. Blog (29th May 2025) (available at https://ukconstitutionallaw.org/))