It has become something of a tradition in British politics: an incoming prime minister promises to restore proper cabinet government. They vow to go back to the good old days of NHS policy being run by the health secretary, schools policy by the education secretary — and decisions taken in open discussion with a prime minister who is first among equals.

The reality, however, is that a small clique in No. 10 ends up controlling the government. Gordon Brown made a fuss about bringing back cabinet government to try to differentiate himself from Tony Blair. In a rare admission of error, Brown says in his memoirs that he failed to do so. He tried to do everything himself, with mixed results. David Cameron wanted to contrast himself with New Labour’s sofa government, and so emphasised how he would govern in the traditional manner. Coalition complicated that plan, and the country ended up being run by a ‘quad’ made up of Cameron, Nick Clegg, George Osborne and Danny Alexander. Even when the Tories did win a majority in 2015, Cameron did little to resurrect a more formal style of government.

Theresa May restored the form of cabinet government, but not the substance. Even as her premiership draws to a close, cabinet meetings often go on for three hours as she ensures that everyone has their say. But the really big decisions have continued to be taken elsewhere. The red lines that May set out for the Brexit talks were decided well away from the cabinet. The 2017 Tory manifesto was launched with almost no one in her cabinet having seen the whole document. The joke then was that May’s cabinet acted as a rubber stamp — hit by a hammer.

Boris Johnson has not made a big song and dance about bringing back cabinet government. But unlike so many of his predecessors, he really might do it. As one of those who knows him best puts it: ‘His natural approach is to delegate, to let other people do things.’ When editing this magazine, and running City Hall in London, his skill was to hire and inspire talented people and let them get on with it. He is the opposite of a micromanager.

The leadership contest has been a reminder that Boris Johnson is not really a details man either. He appears nervy when pressed on facts, something that was particularly evident in his BBC interview with Andrew Neil. As prime minister, his best way of dealing with such questions will be to set out the bigger picture, while referring the detail to the relevant cabinet minister.

Such an approach can only work if these cabinet ministers are not just placemen, but actually in charge of their departments. This places a premium on competence (not a criteria that every prime minister insists on). The government needs ministers who won’t have to have their hands held by No. 10 and are capable of handling a brief. Given how Brexit will consume No. 10 and its energies, these ministers will have to put meat on the bone of Prime Minister Johnson’s domestic agenda.

If a Boris government does intend to let a thousand flowers bloom, there will be problems. No. 10, as an institution, likes being in control. The prime minister gets the blame when things go wrong, it’s said, and ministers hog the credit when they go right. This tendency will be exacerbated under Boris Johnson by the fact that his cabinet will be stuffed full of leadership contenders. Johnson’s age and vintage — he is 55 and first entered parliament in 2001 — means that a large chunk of the cabinet will have their eye on succeeding him as Tory leader. There’ll be those around No. 10 who’ll say that loosening the reins will simply allow his potential successors to push themselves forward.

A Prime Minister Johnson should be relaxed about this, though. He is such a big personality that he isn’t going to be overshadowed by any cabinet minister. When he was mayor of London, he trusted in a set of deputy mayors — who were often more responsible for the policy successes than he was. However, Boris’s pull meant that everybody talked about him. He inherited the policy of renting bicycles in the city, but everyone referred to them as ‘Boris bikes’.

Proper cabinet government doesn’t just mean letting ministers do their jobs. It also requires all major decisions being taken in cabinet. This is harder to do now that there are so many ministers: 29 sit around the cabinet table today, down from 33 during the coalition years, but larger than the 22 when Margaret Thatcher came to power. A cabinet of such size makes proper discussion very difficult: would you invite 20-odd people to a meeting and expect them to come to a conclusion?

I understand that Johnson is being urged to cut the numbers of those attending cabinet to try and ease this problem. Yet, this would only help at the margins; there’d still be more than 20 people at the table. Cabinet committees would have to do much of the heavy lifting on Brexit decision-making.

Modern politicians are overly concerned about talk of splits. If a cabinet is to serve its proper function, it must be representative of the governing party — and not just one faction of it. This will mean that there will be arguments before an agreement is reached. However, this process means that its collective decisions are more likely to bind the rest of the parliamentary party. This is why Boris Johnson should aim for as broad a cabinet as is compatible with his 31 October deadline for Brexit.

One can make many criticisms of Theresa May. But she cannot be accused of failing to work hard enough, nor that she lacks attention to detail. Her failure demonstrates the need for a different approach to the job, one that is more akin to a chairman of the board than a chief executive. This is the approach that would suit Boris Johnson best. But it means that when he chooses his first cabinet, in a few days’ time, he will have to be a meritocrat rather than a leader who just rewards his old pals.