The prime minister has special powers of patronage. The most significant is the power to appoint government ministers. Other patronage powers include:

■ Life peers. The prime minister can appoint people to the House of Lords as life peers. They may include former MPs or party supporters who have made significant contributions in other areas of public life. An independent Appointments Commission makes recommendations on non-party appointments to the Lords, but the prime minister makes political nominations. The power to nominate life peers enables prime ministers to alter the party balance within the Lords. Blair increased Labour’s representation in the Lords by appointing162 Labour peers. The prime minister may nominate life peers with a view to giving them ministerial positions. Gordon Brown gave government portfolios and life peerages to five prominent public figures who were not politicians, including former Confederation of British Industry (CBI) head Sir Digby Jones.

■ The honours system. A police inquiry into allegations of ‘cash for honours’ — that donors to the Labour Party were rewarded with peerages — ended in 2007 without criminal charges being brought. But it led to changes to the prime minister’s role in the honours system. Nominations are now considered by honours committees made up of civil servants and people independent of government. The prime minister accepts their list. In cases where a nominee has donated to a political party, the committee considers whether they are deserving of an honour regardless of the donation.

Powers of patronage in other areas have also been curtailed. The prime minister now plays no role in judicial appointments and is given only one name to approve for ecclesiastical appointments.

Appointing cabinet ministers

The prime minister’s power to appoint and dismiss government ministers, particularly at cabinet level, provides a crucial advantage over colleagues. In theory, prime ministers can create a cabinet in their own image, rewarding supporters and penalising disloyal MPs. In practice, the prime minister does not have a free hand.

The 2010 coalition agreement required Cameron to appoint five Liberal Democrats to his cabinet but all prime ministers face informal constraints on their choice of ministers. A prime minister is, for example, unlikely to overlook senior party figures, some of whom may be rivals for their job. Brown agreed not to stand against Blair in the 1995 Labour leadership election and in return received assurances that he would become chancellor of the exchequer in a future Labour government. Blair was required by Labour Party rules to select his first cabinet (in 1997) from those previously elected to the shadow cabinet by Labour MPs.

In 2016, 15 ministers who had attended cabinet under Cameron, including George Osborne and Michael Gove, were not appointed to May’s first cabinet. Some commentators saw this as a sign of May’s authority, while others noted that those dismissed could make trouble on the backbenches.

Ideological considerations are also important when the prime minister is appointing cabinet positions. A cabinet that contains politicians from only one wing of a party may not have the full support of that party.

Margaret Thatcher included both economic ‘dries’ (Thatcherites) and ‘wets’ (one-nation Conservatives) to her first cabinet, but gave the key positions to her allies. New Labour politicians dominated Blair’s cabinets but Old Labour was appeased by the appointment of John Prescott as deputy prime minister. Most ministers in Theresa May’s first cabinet had campaigned to remain in the EU in the 2016 referendum, but Leave campaigners Boris Johnson, Liam Fox and David Davis were put in charge of departments that would deliver Brexit.

It may also be desirable to appoint ministers from different parts of the country and to include both MPs with significant experience or expertise and younger rising stars. Overall, the choice of ministers will be constrained by the talent available and a party that has had a long spell in power may become stale.

Cabinet reshuffles

Prime ministers can also reshuffle cabinet portfolios. Some ministers might be moved to another post and others dismissed entirely. This allows the prime minister to promote successful ministers, demote those who have underachieved, and freshen up the team. The prime minister decides the timing of a cabinet reshuffle but a sudden resignation may force an unwanted reshuffle. The power to dismiss cabinet ministers can backfire. A botched reshuffle may raise questions about the prime minister’s judgement, reveal cabinet divisions and highlight policy failings. This was true of Harold Macmillan’s 1962 reshuffle, dubbed the ‘night of the long knives’, in which he sacked seven cabinet ministers. Margaret Thatcher’s demotion of foreign secretary Sir Geoffrey Howe in 1989 had damaging consequences because his resignation a year later triggered Thatcher’s downfall.

Occasionally, senior ministers may thwart a prime minister’s plans by refusing to change posts. Gordon Brown planned to make Ed Balls chancellor of the exchequer in 2009, but the incumbent, Alastair Darling, let it be known that he would refuse to accept another post and Brown relented. Weakened after losing seats in the 2017 general election, May shelved plans to dismiss senior ministers. In the coalition government, David Cameron nominated Conservative ministers and Nick Clegg Liberal Democrats. Given this complexity, Cameron carried out only two major reshuffles.