Cameron Brown is a former special adviser at HM Treasury and is now a senior adviser at Charlesbye Strategy.

Anyone who believes Christmas starts earlier each year should spend some time inside the U.K. Treasury.

When the country hears the first faint echoes of Mariah Carey drifting through the supermarket PA system in mid-November, retailers call it the “Christmas creep.” Westminster gets something far less jolly: the “budget creep.” The annual moment when rumors fatten, hints mutate, and half the fiscal package appears to be public before the chancellor has typed a single word.

I saw this more closely than most. Within a single extraordinary fortnight, I went from serving Liz Truss’ first Chancellor Kwasi Kwarteng to working with his successor Jeremy Hunt, moving from the budget that blew up the bond markets to the one built to calm them.

Few advisers get to serve a chancellor who detonates a budget, as well as the one brought in to steady the ship only days later. And there is no better crash course in the life cycle of a budget: the whispers, the over-interpretation, the panic, the denial and the sudden transformation of every think tanker with a spreadsheet into a clairvoyant.

Once that ambiguity takes hold, human nature does the rest. We aren’t built to tolerate secrets. Tell people they will hear nothing until a fixed date, and every stray comment starts to glow with imagined significance. A throwaway remark from a minister becomes a coded signal; an economist’s speculative prediction on X becomes an afternoon of fiscal sleuthing.

But the problem isn’t journalism or the widespread speculation, it’s a system that asks the country to stare at a locked door for months and then expresses surprise when people try the handle. And when you can see the real-world consequences — from hiring freezes and delayed investment decisions to families cutting back their groceries — watching the country whip itself into a frenzy over phantom tax measures isn’t charming.

Inside the Treasury, meanwhile, things look stranger still. Budgets appear to be grand set pieces, but the real action begins six weeks earlier, with the Office for Budget Responsibility’s (OBR) first forecast. Hidden inside is the number everyone fixates on: the sacred “headroom.” In theory, this figure shows what the chancellor can spend without breaching her fiscal rules. In practice, it behaves like musical chairs, constantly shifting until the music stops and everyone solemnly treats the final figure as destiny despite the fact that it is based on projections five years out — as though pandemics, wars and global shocks politely submit advance notice.

During one budget under Hunt, for example, the initial OBR forecast suggested we might have extra breathing space. A senior official murmured: “We might be able to do something interesting” — which, in Treasury culture, counts as reckless hedonism. Then, only days later, gilt yields twitched, growth was revised down, and the headroom shrank like a wool sweater in a boil wash. Outside commentators insisted the chancellor had changed strategy, while it was simply the arithmetic tightening its grip.

By the time the country reaches peak excitement, however, the budget is pretty much at the printers. Two weeks before the speech, the Treasury must submit its major measures to the OBR, so they can be modeled. And once that happens, the concrete sets. Chancellor Rachel Reeves isn’t hunched over a laptop rearranging tax bands like chess pieces at 3 a.m. the night before.

Still, the theater endures. Hence the lasting allure of the so-called “budget rabbit” — a move former Chancellor George Osborne had perfected with a “one more thing, Mr. Speaker” flourish. Kwarteng, on the other hand, attempted the same trick with a cut to Britain’s top tax rate, only to conjure the only rabbit in history that bit the magician and set fire to the stage.

This is why pitch-rolling has become so routine and normalized. It is the quiet art of easing people toward an unpopular measure, so that nobody falls off their chair when it appears. Not because the Treasury loves theatrics, but because surprise decisions can jolt markets. Contentious measures are now introduced gently over time, so Bank of England Governor Andrew Bailey doesn’t have to ring the Monetary Policy Committee for an unscheduled catch-up.

Much of what looks like leaking is simple deduction. Anyone with a calculator, the Treasury’s publicly available ready reckoners and a feel for the political weather can narrow the options. Rule out the unaffordable, cross out the implausible and what remains points in one or two directions.

But silence is no safer. Each year someone proposes the Treasury adopts a genius strategy of saying nothing at all. And while ideal in theory, in practice, this creates a vacuum for paranoia to rush into. Deny one rumor and its opposite becomes gospel; deny nothing and silence becomes a knowing wink and a nudge. Leave a wild claim like “doubling VAT” unchallenged for a day, and you will spend the next week hosing down hysteria from MPs and the public — and rightly so.

Treasury officials are right about one thing, though: Some tax ideas should never be aired, even when they’re being actively developed. Certain measures trigger such powerful behavioral responses that the responsible course is to deny them outright. Whisper “stamp duty cuts,” and the housing market freezes. Float a hint about dividend reform, and accountants begin rearranging client affairs before the budget team has even met. And as Reeves is discovering, even the faintest suggestion of a wealth or exit tax sends globally mobile individuals browsing one-way flights to Dubai.

This reveals a deeper problem. Our tax system is being contorted to satisfy arbitrary five-year windows built on forecasts nobody can honestly pretend to believe. Chancellors end up ratcheting up the tax burden not because the policy case demands it, but because the spreadsheet does. As long as fiscal policy is chained to these crystal-ball projections for 2029, we will keep making real-world decisions to appease an unknowable future.

And yet, as flawed as the current system is, it is still preferable to what came before. Former Labour Prime Minister Gordon Brown’s era of fiscal optimism involved forecasts for an economy that existed only in the minds of ministerial speechwriters, as growth, investment, tax receipts — everything floated serenely and implausibly upward year after year. The OBR was designed to bring sobriety.

Having lived through the best and worst of this process, I can say the real problem isn’t the speculation itself but a system built on projections that collapse at the smallest market movements. We keep trying to deliver tax policy inside an artificial window, dictated by a forecast that’s out of date before the ink dries, and then act surprised when ministers reach for ever higher taxes to satisfy a number that was never real in the first place.

Until that changes, the ritual will repeat. The numbers will wobble, rumors will swirl and the budget creep will appear early. My advice is simple: Abandon the crystal balls, stop pretending the future can be modeled to the nearest decimal place, and let the chancellor get on with governing before the music stops.