A shake-up of government departments might make headlines – but voters need changes that will affect their lives

Inside Westminster: Rightly or wrongly, many people who voted Tory believe that finally getting Brexit done will have a noticeable impact

New year, new government. Boris Johnson is planning a wide-ranging cabinet reshuffle soon after the UK leaves the EU on 31 January, together with a shake-up of government departments.

In my experience, changing the nameplates and moving the Whitehall furniture around normally has little impact. Changes are often rushed, and made to fit round the ministers, rather than getting the departmental structure right first.

Like life, government goes round in circles. Two departments set up by Theresa May on becoming prime minister (for exiting the EU and international trade) will be abolished by Johnson. Trade will become part of a super ministry based on the Business Department; tipped to head it is Rishi Sunak, a Johnson favourite, currently number two at the Treasury.

May’s decision to put climate change in the Business Department will probably be reversed, so it becomes free-standing again, to give the issue symbolic importance. Johnson is considering a controversial move to put the Department for International Development, created by Labour in 1997, back under the Foreign Office’s wing, which would be a pity since it is admired round the world.

It usually takes at least two years for such changes to bed down. The Institute for Government puts the direct cost of a new department at about £15m, plus £34m in loss of productivity as staff adjust. “If done for the wrong reasons or planned poorly, these can result in more problems than they solve, and come at a high cost,” it says.

Once his reshuffle is done, Johnson should leave his ministers in place for as long as possible. The turnover is too high as it stands: we have had nine housing ministers, seven justice secretaries and six work and pensions secretaries since the Tories won power in 2010.

Dominic Cummings, the PM’s influential adviser, wants to put a rocket under the civil service to improve its efficiency. Officials are anxiously poring over Cummings’s speeches and blogs for clues; they have had some discomforting Christmas reading. “Almost no one is ever fired. Failure is normal, it is not something to be avoided,” he said in 2014. He wanted to “get rid” of the role of permanent secretary, railing against a system which “promotes people who focus on being important, not getting things done”.

Cummings is right to argue that there is room for improvement. But Johnson should not be tempted down the route of an American-style politicisation of the civil service, or removing officials who don’t tell ministers what they want to hear. Better to work with the grain rather than declare war on Sir Humphrey from Yes Minister, who can still frustrate the best laid plans.

Ultimately, Johnson will be judged not by headlines about bold reshuffles or Whitehall reform, but by whether he delivers for the Tories’ new working class voters in the north and midlands. His allies admit privately the government’s biggest challenge is to show tangible improvements in the “left behind” towns in the next three or four years. “We are still only at first base on this,” one admitted.

Plans to change Treasury rules, so it approves infrastructure and business projects which improve the wellbeing of people in the regions as well as national economic growth, will correct the bias against the north. This is a big, long overdue reform; the current system sucks investment into the already prosperous south. The IPPR think tank calculates that over the last 10 years, average annual public spending on transport has been £739 per head in London, and £305 in the north.

Finding the money for building projects will not be the problem. But finding quick wins will be. Rundown high streets will not be transformed overnight. Rail and road improvements, attracting more business investment and housing and planning reforms will take years to bear fruit. Despite the cushion of his big majority, Johnson will find that the clock ticks down very quickly to the next general election.

The scope for public disillusionment is huge. Rightly or wrongly, many people who voted Tory believe that finally getting Brexit done will bring a noticeable improvement to their daily lives. To win, Johnson encouraged such great expectations.

Fulfilling them will be much harder. Improving public services and tackling cost-of-living issues will be difficult; budgets for day-to-day spending will be much tighter than for building projects funded by borrowing.

Johnson will find he has much in common with Tony Blair, who frustratingly complained that he “pulled the levers in Whitehall” but found that nothing changed on the ground.

Despite enjoying an even bigger majority than Johnson, Blair never stopped fretting about the next election. I’m sure Johnson, too, will run a permanent campaign, the power of which should not be underestimated by his opponents.

But if things don’t get better, people will know who to blame, and they will. Johnson will find it very hard to maintain the support of his new friends in the north.