John Healey has been publicly framed as a man so paranoid about budget leaks that he imported defence-style "compartmentalisation" to stop the Treasury's financial secrets from escaping. The macho military analogies began in mid-August, when the Telegraph reported Healey was "on a war footing" to halt the drip of information he believed had beleaguered Rachel Reeves. The Financial Times added that "military-style protocols" were in play, the Spectator got excited about "classified computer systems," and the i newspaper described officials signing in to only their own sections of the document, barred from the parts they weren't working on. This weekend, the Observer reported Healey was "flabbergasted" by the lack of security around financial information when he became chancellor, noting it was "so different to how we did things in the MoD."

The chancellor is known to have worried that market-sensitive leaks cost Britain billions in the run-up to the last government's budgets. But has this time around really been so different? Despite the heightened "security" around Wednesday's budget, many of its announcements have already leaked from a clear mixture of authorised and unauthorised sources.

It emerged well in advance that there will be a higher tax on banks - a deeply market-sensitive policy - and a package of energy support for the most vulnerable. There will also be billions of pounds in extra defence spending, directed towards the British Business Bank and National Wealth Fund, plus a £1bn crackdown on online VAT sales, with big retailers such as Amazon, eBay and Temu made responsible for collecting what is due from smaller merchants selling on their platforms. On top of that, stories have indicated the level of headroom the chancellor will be looking at - in the region of £15bn - known in the political trade as "pitch rolling" to avoid alarming the markets or the public.

The Treasury and No 10 have also undertaken their traditional stream of embargoed announcements by press release in the days before the fiscal event, such as a new £1.5bn borrowing facility for local authorities and £1bn for social housing, as they seek to build a sense of action and momentum about what the government is trying to achieve.

Former Treasury advisers believe the rigmarole around budget security is partly designed to deter civil servants and gossiping MPs from thinking they can embark on unauthorised chatter before a policy is ready. But they also say it is unhelpful for the chancellor to produce a hermetically sealed budget, which could cause a backlash over surprise measures - in the markets, the media, among the government's own MPs and the wider public. It is often the less-trailed policies that have tended to go wrong, from George Osborne's pasty tax in 2012 to Philip Hammond's surprise national insurance hike for the self-employed in 2017 that had to be abandoned within seven days after a furore among Conservative MPs about breaking their manifesto promise.

Aides say there is a balance to be struck - and it's not always a good idea to hoard information until budget day. "If everything is kept tight, then you end up surprising people. And that's called a Liz Truss situation," says one former strategist from the Tory years. Healey has been shutting down speculation about various tax rises, from higher capital gains tax on certain assets to lowering the mansion tax on properties worth more than £1.5m - showing he has begun to see the virtue in expectation management and limiting surprises on the big day.

There may still be a few fiscal "rabbits out of the hat" on the day, as Healey seeks to combine a "steady-as-she-goes" budget with some eye-catching measures designed to show the public that the government is on their side. But if the Treasury really has aimed for military levels of secrecy around its budget, the Ministry of Defence might have something to worry about.