The beer is going a little flat as tensions surface between No 10 and No 11

There is no more important relationship in government. When prime minister and chancellor are working in harmony, their combined forces can be irresistible. When the first and second lords of the Treasury are at odds, crockery gets broken – and sometimes careers. Andy Burnham and John Healey should know this better than most. As younger men, they both had ringside seats for the most durable marriage of the postwar era between the Downing Street neighbours.

The partnership between Tony Blair and Gordon Brown was hugely productive. Had it not been, Labour would not have won three elections on the trot. It was also fiercely argumentative. When prime minister Blair went on Sunday morning television and declared that a big boost in health spending was on its way, chancellor Brown raged at him: “You’ve stolen my fucking budget!” The eruptions were so frequent that Whitehall coded the rows as “the TB-GBs”.

And that was at a time when life looked sweet. The economy was expanding at a decent lick, tax and spending decisions were a whole lot easier than they are today, the White House wasn’t occupied by a maniac and there was no conflict in the Strait of Hormuz. Mr Healey, who was a junior minister at the Treasury during the Brown years, waxed nostalgic about that blissful period during his recent party conference speech, only then to acknowledge “the money New Labour had in the 90s is simply not there now”.

Related articles: Healey plans deep energy reforms to cut Britain’s bills The Standard of Living is all to play for as Healey prepares for first budget Adversity can bind the neighbours together. Roy Jenkins used to remark that he and Harold Wilson tended to be closer when they had their backs against the wall. Hard times can also drive them apart. Relations between Theresa May and Philip Hammond became poisonous because they were not strongly attached to each other.

Chancellor Healey and prime minister Burnham share similar soft-leftish politics and agree that provincial England, especially the north, has been short-changed for years. “They have a similar strategic view of where the country needs to go,” says one ally of the chancellor, pointing to his record of supporting devolution. Both are products of Cambridge University, though of different vintages. Both have been doing politics for donkey’s years.

What they are not is staunch and long-standing confederates who jointly forged a project for government. They are not like Margaret Thatcher with Geoffrey Howe, Messrs Blair and Brown, or David Cameron and George Osborne. The chancellor is 66. He is much nearer the end of his career than its beginning and thus much less likely to pose any kind of threat to the guy next door. The rumour mill whispers that there was a cynical bargain. Mr Healey dealt the coup de main to Sir Keir Starmer by unexpectedly resigning as defence secretary over the then prime minister’s refusal to commit to raising defence spending to 3% of GDP by 2030.

Sir Keir was toppled. Mr Burnham replaced him and promptly promoted Mr Healey to the second best job in government. Suspicious, no? Team Andy protest there wasn’t a plot. They insist that Mr Healey landed the role because the prime minister found him capable, equable, inoffensive to any of the Labour factions, and a man he thought he could trust. Social media video of “Andy and John” bantering about Twiglets, scampi fries and pork scratchings in a pub certainly looks more natural than when “Tony and Gordon” had to pretend to like each other for TV cameras.

Aides report that prime minister and chancellor have thrashed out details of the budget over Sunday evening curries and alcohol-lubricated one-to-ones that have been nicknamed “beerlaterals”. If they have exchanged any profanities, they have yet to reach the ears of journalists. They have avoided the febrile torrent of destabilising leaks that preceded both of Rachel Reeves’s budgets. Aides say Mr Healey was “flabbergasted” by the lack of security around sensitive information when he became chancellor.

“It was so different to how we did things in the MoD.” The introduction of military-style protocols has compartmentalised access to budget secrets. Sceptics wonder whether little has leaked because there is not all that much to disclose. One Labour strategist observes that ‘as a newbie chancellor’ Mr Healey will want to ‘buy himself some space and some credibility’ One Labour strategist observes that ‘as a newbie chancellor’ Mr Healey will want to ‘buy himself some space and some credibility’ There have been revealing sparks of friction.

When the chancellor suggested to a television interviewer that the prime minister was running a “continuity government” there was strong pushback from Number 10 at the implication that Mr Burnham is Sir Keir with prettier eyelashes. Much of the tension derives from where they sit. As chancellors are wont to do, Mr Healey stresses about the fragility of the national finances and worries about the beating his reputation will suffer if he fluffs his first budget.

One Labour strategist observes that “as a newbie chancellor” he will want to “buy himself some space and some credibility”. Easier said than done. Forecasters reckon that at least half of the £24bn of fiscal breathing space he was bequeathed by his predecessor has been wiped out by higher inflation and increased government borrowing costs. His repeated stress on his commitment to the fiscal rules has friends of Ms Reeves wryly noting that many of his lines are identical to the ones she used to trot out.

The buzz phrases used by Treasury insiders to describe the forthcoming budget are all synonyms for caution. “Do no harm”. “Tightly focused”. “Low-key”. “Steady-as-she-goes”. These prudent catchphrases jar with the expansive – and expensive – commitments that the prime minister is fond of making. Some Burnham allies can already be heard chuntering that Mr Healey has been taken prisoner by the “Treasury brain” with its fiscal orthodoxy and institutional conservatism.

The main concession to the prime minister’s agenda is that this will be billed as a cost-of-living budget. I’m told that the tagline on the front of the budget document will be: “Breathing space for today, fresh hope for the future”. You’d be right to expect modest measures designed to ease the pressure on poorer and middling households. It doesn’t sound like it is going to be a big-bang budget that attempts to unpick the “40 years of neoliberalism” that the prime minister inveighs against.

Unless we have all been wildly misdirected, this is not going to be a game-changing event that dramatically resets the trajectory of the country. Some will probably castigate it as boring. That will aggravate both Number 10 and the Treasury. I grant you that no one likes to be called dull, but this is not the most damning verdict a budget can receive. Just ask Liz Truss and Kwasi Kwarteng, a duo who were anything but boring and anything but successful.

Photograph by Ian Forsyth / Getty Images Andy Burnham Budget John Healey