Theresa May and Philip Hammond have been described as being 'like an old married couple' © Stefan Rousseau/PA

Philip Hammond, Britain’s chancellor, wants his first Budget on Wednesday to present a solid, uncluttered view of how to prepare the economy for life after Brexit.

But the fingerprints of Theresa May, the prime minister, and her team are on some of the measures that have been announced in advance, including a £500m package that could herald greater selection in state schools.

Few believe, for example, that Mr Hammond was the author of a new policy to hand out £6m to pay for buses or taxis to take disadvantaged students to existing selective schools.

Number 10’s interventions seriously annoyed the 61-year-old former businessman last November, at the time of the Autumn Statement. “He felt they were all over him,” says one friend.

But those close to Mr Hammond and Mrs May insist that last year’s lessons have been learnt, saying they were the result of inexperience: the May administration was only a few months old.

Number 10 officials say the preparation of this year’s Budget has been “transparent”. Whatever the tensions between officials at the Treasury and Mrs May’s team, both sides use the word “respectful” to describe relations between the principals.

Mr Hammond’s friends say he has no wish to run a political empire from the Treasury or to announce policies for other ministers. He wants to run a serious operation for serious times. “Boring is good,” he advises colleagues.

“The Treasury hasn’t got the firepower to use a fiscal event to dominate the political agenda for the next nine months,” said one minister.

On fiscal strategy, the chancellor has fended off a clamour for unfunded spending increases: instead insisting that new money for education, social care and business rates relief be offset by tax rises or savings elsewhere.

Meanwhile, Mrs May has backed his central judgment that any good fiscal news should be banked to build up his £27bn “war chest” in case Brexit goes wrong. “They are both fiscal Conservatives — they both want a balanced budget,” said one Treasury official.

The Budget will also outline domestic policy reforms that could become hallmarks of Mr Hammond’s tenure at the Treasury: sustainable funding of social care, business rates reform, employment tax reforms, better technical education.

The chancellor is also happy to share — within reason — the drafting of his Budget with a prime minister whom he has known since university days. “They are like an old married couple,” says one observer.

The neighbours dine together regularly, sometimes with their spouses, while one colleague said wryly that their exchanges at the cabinet table carry a familiarity that could sometimes “almost be described as banter”.

But Brexit has caused strains. On several key calls, Mrs May and her team of former Home Office advisers have prevailed: controlling immigration and leaving the jurisdiction of the European Court of Justice are red lines. Despite deep Treasury misgivings, Britain is leaving the single market and customs union.

George Osborne, Mr Hammond’s predecessor, last month delivered an icy assessment of Mrs May’s Brexit strategy: “The government has chosen — and I respect this decision — not to make the economy the priority.”

Mr Hammond, who tried to keep open the option of staying in the customs union, has however been adept at winning battles with Number 10 where he feared there was a risk the government could make a bad situation even worse.

While Mrs May and her team took Brexit as a sign that voters wanted to tame global capitalism, Mr Hammond took the opposite view that if Britain was leaving its biggest market, it needed to prove it was still open for business.

The chancellor, an economic liberal, went along with most of Mrs May’s industrial strategy, but succeeded in deleting some of the policies with which the prime minister had previously been associated.

Mr Hammond resisted the idea of placing workers on company boards, strict limits on executive pay and suggestions of a much more restrictive foreign takeover regime. “We’re not going down the Danone route,” he said, referring to French attempts to protect the “strategic” yoghurt company.

There are new areas of difference. Mrs May and Greg Clark, business secretary, want to protect “loyal” energy company customers who are moved to expensive standard tariffs, while Mr Hammond believes consumers should shop around.

Mr Hammond has also rejected the idea of a “death tax” to fund social care, although it remains one of the options being considered by officials reporting to Mrs May.

Nevertheless the chancellor approaches his first Budget day in good spirits, laughing off suggestions that healthy tax receipts could put pressure on him to open the spending taps. “I’ll deal with that problem,” he tells colleagues.

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