Labour MPs must decide where their loyalties lie in a Corbyn-led cabinet - as must Corbyn himself

Leadership and loyalty is one of the great Shakespearean themes. To whom, or to what, is a leader loyal? Do his or her personal convictions matter most? Must a leader be loyal to close friends and allies? Is there a wider loyalty to the party and the country that can conflict with a leader’s other deeply held principles?

Already the leadership of Jeremy Corbyn is a Shakespearean epic. Corbyn is being tested – but so too will those internal critics being feted by a media hostile to the new leadership. And where do their loyalties lie?

The appointment of John McDonnell as shadow Chancellor is making big waves. There are many Labour MPs who cannot quite believe their economic policy will be framed by a figure that some regard as being to the left of Corbyn. They are in bewildered despair. Ed Balls had worked 18 hours a day since 1993 navigating the wild seas of economic policy for Labour; McDonnell pops up as if from nowhere.

In recent days, various sympathetic figures had urged Corbyn to appoint Angela Eagle, a former Treasury Minister and a far less provocative appointment. But reflect for a moment on loyalty and the appointment is wholly understandable. McDonnell is a close friend of Corbyn’s and one with a long interest in economic policy. With a more overwhelming mandate than the one secured by Tony Blair in 1994, Corbyn is in a strong enough position to be loyal to his convictions and his friend. He would have been disloyal to both if he had not made the appointment.

McDonnell’s elevation is almost as remarkable as Corbyn’s, but for a leader who stood and won with an alternative economic policy forcefully advocated by McDonnell it would have been even more surprising had Corbyn not made the appointment. A new leader is never stronger than at the beginning. This is a moment for Corbyn where loyalty can be relatively uncomplicated.

Making McDonnell his shadow Chancellor must have been as obvious for Corbyn as it was when Tony Blair made Gordon Brown his in 1994, his close friend who had focused much more closely on economic policy. The fact that Corbyn hesitated, with some of his advisers urging him not to take the risk of appointing McDonnell, shows that the new leadership is at least a little sensitive to the hugely complex political world it has entered.

Corbyn has gone some way to selecting a politically balanced front bench. The lack of women at the top looks awful – but it is not his fault that party members appointed a male deputy and a male mayoral candidate. He cannot be blamed, either, for the complex reasons Harriet Harman, Yvette Cooper, Liz Kendall, Caroline Flint and Rachel Reeves choose not to serve in the Shadow Cabinet.

As far as a leader is concerned, loyalty takes many forms and can change depending on the political context. Even with a landslide majority, Tony Blair sacked his close friend Peter Mandelson twice, at least one of the dismissals being unfair. In the face of a media onslaught against Mandelson, Blair did not feel strong enough to remain loyal. Corbyn will be unmoved by media onslaughts as he works on the safe assumption he will not get a fair hearing. Blair felt, perhaps rightly, that having a supportive media was a precondition to electoral success. Mandelson was sacrificed on that basis.

So Corbyn’s test will come as he faces the wider responsibilities of leadership. When Neil Kinnock was interviewed in the late 1980s, he was asked: “As leader of the Labour party, what is now your personal view of unilateral nuclear disarmament?” Kinnock replied: “As leader of the Labour party, I am not allowed personal views. Personal views and being leader of the Labour party are almost a contradiction in terms”.

There is an illuminating discussion between Kinnock and his former head of staff, Charles Clarke, in a new book, British Labour Leaders, which Clarke co-edited. For the first time in public, the duo reflect on the turbulent years in which they worked together at the top of their party, the nightmarish dilemmas and impossible conundrums. Corbyn should read it, and so should others quick to criticise leaders; leadership is not easy.

Over time, Corbyn will not be as strong as he is in the aftermath of a triumphant win. He will have to accommodate and compromise. Kinnock had done a lot of that before he became leader; until Saturday, Corbyn’s only loyalty was to his beliefs.

Disillusioned Labour MPs agonise over where their loyalties lie now. Some have thought hard about whether to join the Shadow Cabinet. A few agonised and were then never asked to join. Some have said publicly they did not want to do so. Convinced that Corbyn cannot win, they argue that they have a loyalty to their constituents in seeking a Labour government. But asserting such a loyalty is the easy bit: they also have to decide what they stand for and whether, in expressing opposition to a leader, their disloyalty becomes part of a self-fulfilling prophecy.

Election results and polling will determine what form the loyalty of the leader and his dissenters will take. If Labour falls miles behind in the opinion polls Corbyn will not have the strength to be as loyal to his principles and his allies as he has been this week. If voters approve of him the dissenters will have little choice but to rally round. The stakes are high. If the Conservatives win in 2020 they will have ruled for 15 years. Under a five-year fixed-term parliament, a tiny victory delivers power for a long time. Winning elections is the ultimate responsibility of a leader of an opposition and also of those below him who, in wrestling with their convictions, know that openly divided parties are doomed to lose.