Reports describe defence-style budget secrecy at the heart of government, with John Healey said to have set up compartmentalisation designed to stop the Treasury's financial secrets escaping - and the military analogies beginning as far back as mid-August. Yet a long list of budget measures has entered the public domain anyway, from authorised pre-announcements to unauthorised disclosure. With the budget falling on Wednesday, the question is whether the lockdown has changed anything at all.

A war footing at the Treasury

The security operation has been reported in strikingly martial terms:

• •The Telegraph said Healey was "on a war footing" to stop the drip of information he believed had affected Rachel Reeves.
• •The Financial Times reported "military-style protocols" being deployed.
• •The Spectator highlighted the use of "classified computer systems".
• •The i newspaper described a system in which officials could sign in to only their parts of the document.

The Observer reported that Healey was "flabbergasted" by the lack of security around financial information when he became chancellor, telling the paper "it was so different to how we did things in the MoD". He was reportedly worried that market-sensitive leaks cost Britain billions in the run-up to the last government's budgets.

Former Treasury advisers say the operation also aims to deter civil servants and gossiping MPs from thinking they can embark on unauthorised chatter.

The leaks that got through anyway

Despite the heightened security, many budget 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 market-sensitive policy, and a package of energy support for the most vulnerable also escaped early.

Further reported measures include:

• •Billions of pounds in extra defence spending directed towards the British Business Bank and National Wealth Fund.
• •A £1bn crackdown on online VAT sales, with big retailers such as Amazon, eBay and Temu collecting VAT due from smaller merchants.

Stories have indicated the chancellor's fiscal headroom is in the region of £15bn – known in the political trade as "pitch rolling". Meanwhile, the Treasury and No 10 issued embargoed pre-budget announcements of their own, including a new £1.5bn borrowing facility for local authorities and £1bn for social housing.

Healey has shut down speculation elsewhere, including on higher capital gains tax for certain assets and on lowering the mansion tax on properties worth more than £1.5m.

What past budgets say about surprise

Former advisers warn that a hermetically sealed budget could cause a backlash over surprise measures - in markets, in the media and among MPs. History offers the cautionary examples: George Osborne's pasty tax in 2012, and Philip Hammond's 2017 national insurance hike for the self-employed, which had to be abandoned within seven days after a furore among Conservative MPs over a manifesto breach. One former Tory strategist told the report that hoarding information risks catching people unprepared - the kind of surprise associated with Liz Truss.

On Wednesday, it will become clear whether a few fiscal "rabbits out of the hat" survived the lockdown - as Healey reportedly aims to combine a steady budget with eye-catching measures - or whether the secrecy operation has made little practical difference.