WRITING this column several days before the Budget presents something of a problem.

There is little point in trying to predict what the Chancellor might say as you will already know what he actually said.

Given this, I thought it might be interesting to share my own limited experience of what goes on behind the scenes.

The secrecy that surrounds the Budget process is incredibly strict and you can be pretty certain that any leaks are deliberate, either to trail major announcements or to test the potential reaction to something the Chancellor is considering.

I’ve seen the process in action and on a few occasions have been asked for my views.

The first time this happened the document that was handed to me bore the security grading ‘Budget Restricted’.

I asked if I would be required to sign the Official Secrets Act. The answer was a jovial “oh, don’t worry about that – we can prosecute you whether you’ve signed it or not”. I did not feel greatly reassured.

On another occasion I was given a numbered copy and told: “It’s the only copy going outside the building, so if there’s a leak we’ll know where it came from.” I kept a very tight hold on it all the way back to Taunton.

Things can change right up to the last minute.

I was once invited to the Treasury a few days before the Budget, shown into a room and asked to read some draft Budget Day press releases about a fundamental tax change.

I was asked both what I thought the reaction would be and about the mechanics of implementation.

By Budget Day the Chancellor had made a very significant change to what I’d seen.

I can only imagine how much activity there had been behind the scenes in the intervening few days. What was the issue? I’m afraid I still regard myself as being bound by the secrecy surrounding the process.

As I write this, on the Sunday evening before Budget Day, Treasury officials and Ministers will be putting the finishing touches to the Budget papers, but until the day itself, only the Chancellor can be certain of what will be going into that famous red box.

There is one secret I can share however. While the finishing touches are being put to the Budget, somewhere in Whitehall a very special rabbit is being trained to jump out of the Chancellor’s hat.

*Paul Aplin OBE is a tax partner with A C Mole & Sons and chairman of the Technical Committee of the Institute of Chartered Accountants in England & Wales Tax Faculty; you can follow him on Twitter @PaulAplinOnTax. He and fellow tax partner Amanda Gunter can be contacted on 01823-624450.