But the true value of the Brief lay not just in handling the media and Parliament after the event, but spotting in advance those issues where the questions were so tricky and the proposed answers so poor that it gave Ministers and advisers pause over whether this was the right measure after all.

Ed Balls, Michael Ellam and other individuals responsible for briefing the press in the crucial hours after the speech would also be expected to memorise it, or at least give the impression they had all the answers at their fingerprints by turning straight to the relevant section.*

Ministers who would appear in the Commons or in the media to defend the Budget would pore over the Brief in advance - some more diligently than others - to avoid being caught out.

Occasionally under a particular Q&A, there would be a line in bold type, underlined, all caps, and square brackets - just to remove any doubt that this might be sensitive - saying: ’[NB - NOT FOR PUBLIC USE:…’ , alongside which would be an explanation for a curious reader about why we couldn’t give a straight answer to a particular question and needed to stick exactly to the formula of words proposed.

Each section of the Brief, carefully colour-coded and divided, written across two columns and both sides of an A4 sheet, would follow the same headings: Issue; Summary; Points to Make; and Lines to Take, the latter by far the biggest section as this was where the tricky Q&A was contained.

A very large ring-bound folder, never meant for public consumption, it contained in one place all the points to be made and questions that could conceivably be asked about each and every Budget measure, about the fiscal arithmetic and forecast, and about the package as a whole.

Back in my Treasury days, probably the least glamorous part of preparing for Budgets, Autumn Statements and the like was compiling 'The Brief’. If 'The Scorecard’ was where the high-octane action and key decision-making took place in the run up to the Budget, the Brief was the purest drudgery, but no less important for that.

So no wonder the planning has started much earlier this time round. But that’s where a different and even bigger set of political problems kick in.

You could also argue the turmoil caused by cuts in other departments made Cameron, Osborne and co. take their eyes off the ball when it came to Andrew Lansley’s grand restructuring of the NHS, which they now regard as their “greatest mistake” - and that’s even before this year’s looming winter health crisis is hung round their neck.

It’s important to remember the problems that period caused the Tory government, making the 'new lot’ look as incompetent as 'the last lot’ in the public eye, establishing the cuts as ill-considered and reckless, damaging ministerial careers, and creating huge distrust between civil servants and their political colleagues.

And ‘rushed’ is an under-statement. The ink was barely dry on the Coalition agreement before Department for Education officials were submitting proposals to Michael Gove for £1.6 billion of cuts in his budget, asking for “your steers both on broad principles and specific savings identified”.

No-one in Whitehall - ministers or civil servants - wants to experience again the process they went through in the days after the Coalition agreement, where the rushed effort to find £6 billion of immediate cuts for George Osborne’s June 2010 Budget resulted in botched episodes like the scrapping of Building Schools for the Future, or the privatisation of the forests.

And this morning, in what I consider a vastly important development, one or more concerned Cabinet ministers have broken cover to confirm to The Guardian that this cuts-identification exercise is afoot.

The answers varied from classic Sir Humphry: “It might be considered surprising were we not” to budding Malcolm Tucker: “What the f*** do you think?”

Over the last month, I’ve been asking old muckers in the Treasury and across civil service departments one key question: “Are you already working on the £25 billion?”, by which I meant the further, unspecified cuts in public spending announced by George Osborne at the Tory conference, partly to fund David Cameron’s simultaneous splurge of tax cuts.

In which case, cheer up - because today the party that specialises in self-inflicted wounds blew half its toes off.

After this week’s leadership shenanigans, and their unsatisfactory aftermath , even many Labour MPs and supporters will now think the election is the Tories’ to lose.

If you like, the Brief acted as the Scorecard’s safety net. After all, if expert civil servants and press officers could not come up with concise, convincing answers to questions under no pressure at all before a measure had been announced, what chance did a Minister have at the Despatch Box or Ed Balls briefing the Parliamentary lobby?

Many’s the Budget measure which got all the way through the process, but was jettisoned late on when senior figures saw the Brief, and thought: “Whoa! We didn’t know that was an issue.”

So back to the £25 billion cuts.

If you’d asked me at the time of the Tory conference to prepare a classic Brief-style response to the question: “Where are these cuts going to fall?”, I’d have written the following:

“We will identify these savings as part of the next Spending Review process early in the next Parliament. “It’s not possible to spell out the detail at this stage because there are obviously some savings we would like to make in the future that our Coalition partners would not, so this exercise can only be carried out once we see the shape of the next government. “But having already cut billions of pounds from Whitehall spending since 2010, we believe the British people will accept that this £25 billion figure is achievable without affecting essential front-line public services, and will trust us to deliver it as promised after the election next year.”

End of story, and that’s the line you would sit on no matter what variant of the question was asked. And if some pesky Evan Davis-type asked you about a specific item of public spending, and whether it’s earmarked for the chop in the next Parliament, you would just fall back on that old favourite:

“We have no plans for cuts in that area; this is just more scare story propaganda put about by our opponents to disguise the fact that they are not serious about cutting the deficit.”

If I saw those ‘lines to take’ in the Tories’ pre-election Brief, I’d give them a big tick and move onto the next section: ”…Oh bollocks, immigration".

But unfortunately for the Tories and thanks to The Guardian, tthose lines in the Brief on the £25 billion now have a giant red line through them.

We now know that the Tory Treasury is already working on detailed plans for where the axe will fall, as is each civil service department, other than those whose spending is ringfenced.

The Tories cannot therefore deny that those plans exist, first because it is a lie, and second because of the grave danger that – over the next six months – even one department’s plans will leak to the media, the unions, or the Labour Party.

And believe me, those plans are full of the most horrific spending cut proposals you’ll ever see splashed on the front page of a newspaper.

How do we know?

First, because that’s the only way each department can make the sums add up. Second, because the civil service likes to show that it has thought the unthinkable and imagined the indefensible, if only so Ministers can rule it out.

And third, most importantly, because that’s exactly what happened last time round. What was announced in the 2010 Emergency Budget was bad enough but what was included in the civil service’s initial plans was just monstrous.

Go back to the original May 2010 plan I mentioned from the Department for Education, and we see items like: “Reduce funding to disabled children short breaks by 5 per cent - £10m” , “End free childcare for 2 year olds - £20m”, and “Stopping the Every Child A Reader programme - £56m", all helpfully written in red font so Michael Gove would know they were the more controversial ideas.

That plan also makes clear that the targets can only be delivered by making “at least some level of frontline savings”, even while the rhetoric around the coalition agreement was saying the exact opposite.

I can only imagine what will be in the plans and analysis of the non-ringfenced departments this time round, given they’ve got far less money to play with and much bigger savings to find, but put it this way – Tory ministers and strategists will live in morbid fear of them emerging publicly between now and May.

Yet what on earth do they now say in the meantime? Are they supposed to acknowledge they’ve got secret plans but won’t tell the public what they are? Secret plans are never a good idea going into an election, unless they’re to do something very popular, like end the war in Vietnam.

Because once it’s established that the Tories have got secret plans, Labour can do all the scaremongering it wants about what is in them. And the Tories can hardly deny that scrapping Winter Fuel Allowances or forcing patients to pay for a GP appointment are in their plans if they won’t say what is.

Just imagine…

Osborne: “Sterilising people on benefits is categorically not in our plans. That is preposterous and offensive.” Naughtie: “Well what is in your plans?” Osborne: “I can’t tell you that at this stage.”

And let’s be clear: you can get away with a fair bit of ‘You’ll have to wait and see’ and ‘I’m not going to speculate’ if you’re a Chancellor coming up to a Budget when people expect you to maintain some secrecy. But you can’t do that before an election. Or you can try, but you won’t win.

This is why – unless someone with a better memory of past manifestos corrects me – no party in recent memory has gone into an election promising a specific cash amount of spending cuts they are intending to make but refusing to say what they are.

Certainly not a party that is in government, and can’t even hide behind the need to 'look at the books’ before it takes its decisions.

At the 2005 election, both Labour and the Tories went in promising to cut specific amounts of Whitehall waste by implementing their respective Gershon and James Reviews: the dispute then was only whether their identified savings were achievable in full.

In 2001, the Tory commitment to reduce public spending to a certain percentage of GDP over the Parliament was equated by Labour to a planned cut of several billion pounds, but that argument was largely lost on the public by the time you’d explained the maths.

But this time, the Tories are doing Labour’s work for them by spelling out the cash figure, and they’ve now handed Labour a giant gift by admitting that secret plans to identify the cuts are in the works.

Osborne’s tough promises at the Tory conference on spending cuts and deficit reduction were intended as an election trap for Labour, but have instead turned into a bomb ticking under Tory HQ.

Of course, there’s another scenario here that Osborne plans to unveil the full detail of the £25 billion cuts as the centrepiece of his pre-election Budget, challenge Labour to back them, and ask the British people to approve them, thus pre-empting any of that ‘secret plans’ scrutiny.

If that’s his strategic masterplan, then I wish him the best of luck and look forward to him celebrating one victory in 2015: the honour of writing at least the second longest suicide note in history.