Fear and loathing have triumphed, I have capitulated; I am taking my lump sum tax-free cash ahead of the November budget.

For the avoidance of doubt, I’m not advising you to do the same. Everyone’s situation is unique: take advice, make your own decision. But here’s how I arrived at mine.

First, a few quick relevant facts. I’m 59, I’m already only working part-time, my pension has exceeded the old lifetime allowance and hit the maximum tax-free limit of £268,275. Yes, I have been fortunate in life, but what kind of a pension expert would I be if I hadn’t hit these limits? I’m also not expecting to save much more into pensions in the future and within a few years I’ll be drawing on my savings.

The context is a government painfully short of money and ideologically disposed towards taxing wealth.

There are few other places they can go to find the money they need (other than cutting spending, but that’s another story). And they have also explicitly talked about reducing the tax-free pension allowance.

In short, if ever there were a time when the government might choose to reduce the allowance, it is now, this year, this budget. I know of others in the pensions industry in a similar situation to myself who have come to the same conclusion.

Let’s say the government reduces the tax-free cash allowance from £268,275 to £100,000, as the Institute for Fiscal Studies (IFS) has recommended (although the pensions secretary and Treasury minister Torsten Bell has advocated cutting it down to just £40,000). That would cost me between £33,655 and £67,310, depending on how much of my income gets taxed at 40 per cent.

• Why a tax panic is sweeping through the middle class

Because my tax-free cash is now capped at £268,275, any future growth in my pension is already going to be taxed when it is withdrawn and that allowance is very unlikely to increase.

What’s more, by 2027 my pension fund will also become liable for inheritance tax, so that’s another incentive for keeping money in the pension system that will be gone.

By taking the tax-free lump sum now, I could reinvest the money in Isas for myself and my wife over the next few years. Initially this will result in a loss in gains, relative to leaving the money in a pension to grow.

But both the growth and the subsequent income withdrawals from the Isas will be entirely tax-free. This means that within a few years, I’ll be better off than I would have been just leaving the money in my pension, even if the government doesn’t reduce the tax-free allowance.

If the allowance is slashed, and it turns out that I have slipped through the door before it closes, then I’m quids-in from day one.

• Stick or twist? Savers fear for the pension tax-free lump sum

The one unmanageable risk for me in this calculation is if the chancellor, Rachel Reeves, chooses instead to cap the Isa allowances in some way, either the annual contribution or the cumulative capital amount allowed in Isas (something else Bell has spoken about in the past).

That could leave me with a large bag of money in my bank account and no tax-free shelter in which to park it. I’d then have to pay tax on future growth, barring the modest capital gains tax and interest allowances still available to me.

For me, it is an asymmetric risk though: the cost of not acting now could be £30,000 or more, against the cost of acting, which is likely to be only a few thousand pounds at most.

If I’m wrong and they don’t reduce the tax-free cash allowance, I’m still OK with that; it is a calculated gamble.

• Read more money advice and tips on investing from our experts

I have one further warning for readers. In past years, canny budget watchers have submitted a request to their pension company to withdraw their tax-free cash ahead of the budget. They have then used cancellation rights afterwards to reverse the transaction. The Financial Conduct Authority, the City regulator, and HM Revenue & Customs have issued co-ordinated warnings that such a dodge may not work this time around, due to their interpretation of what constitutes cancellation rights and the one-way nature of some pension tax allowances.

Tom McPhail was the head of retirement policy at the investment firm Hargreaves Lansdown