The leaves are turning brown, the birds are migrating south and the Treasury is briefing out the possibility of raising fuel duty: autumn is coming.

In the last few days, it has been widely reported that the chancellor, Rishi Sunak, is considering raising fuel duty by as much as 5p a litre in the autumn budget. This would be ambitious, even for a political party that did not fetishise the taxable rate of petrol and diesel. So what is the chancellor up to?

The Treasury is fond of “pitch rolling”, a term borrowed from cricket that means preparing the wicket for an important match. Essentially it involves readying the political ground for a potential – and often unpopular – change in policy. Whether this latest leak was from supporters or opponents of the chancellor, what is clear is that ministers have long wanted to increase fuel duty for one simple reason: it raises a lot of money – around £28bn a year – making it the fifth-largest tax.

Given ten years of successive freezes, floating the idea that it could be raised by 5p a litre is not so much rolling the pitch but rather bulldozing the entire pavilion. Conservative chancellors have tried “pitch rolling” a fuel duty increase for the last few years, but at every budget it has remained frozen. I know this because, prior to becoming a journalist, I worked at the Treasury and tried – without success – to increase it.

So why do they do this? The fuel duty freeze was one of the cornerstones of George Osborne’s chancellorship, but it has been extraordinarily expensive. The issue is that the Office for Budget Responsibility, which provides independent forecasts for the government, assumes that fuel duty will rise by inflation every year – despite all evidence to the contrary.

Therefore a fuel duty freeze costs real money. Thus far, successive freezes have cost the exchequer well over £100bn. It is not for nothing that David Cameron referred to Robert Halfon, who has run numerous campaigns on the issue, as the “most expensive MP in parliament”.

How it tends to work is that in late summer, ministers or special advisers brief the press – off the record – that the chancellor is serious this time about increasing fuel duty. Meanwhile, following political steers, civil servants might draft a parliamentary question for a friendly backbencher to table, for the purpose of getting the high cost of a further freeze into the public domain.

But then political gravity reasserts itself. Conservative backbenchers inform the chancellor it would be “madness” to increase fuel duty, sometimes signing letters to that effect. The press meanwhile jumps to the defence of “white van man’”; the Sun has run its Keep it Down campaign since 2011, and can reasonably take credit for successive freezes. Indeed, it has already warned its readers that a 5p increase would cost drivers more than £100 a year.

And so by party conference season, the game is usually up. Occasionally, there are veiled threats that this freeze will be the last. But this is somewhat undercut by what comes next. The media strategy shifts to being a celebration of the policy decision. Officials and ministers find endless ways of calculating how much successive freezes have saved the average driver: per litre, per tank, since the previous year or since 2010. Every statistic imaginable is provided.

It is understandable the government feels that if it is going to continue to pay for this policy, it should at least be able to claim the credit. But the difficulty is that this undercuts all the tentative progress made over the preceding months, making it just as difficult to raise fuel duty the following year.

So why might it be different this time? First, the government has a healthy majority, something absent since 2015. And then there is the impact of Covid-19, which has made the need for revenue greater. Even before the government turned the economy off in March, the outlook for the UK’s fiscal stability was poor. And under the most optimistic recovery scenario, UK public sector net debt as a percentage of GDP is projected to pass 200% by 2060 and 300% by 2070, largely as a result of demographic change – these are the costs associated with an ageing society. The chancellor may no longer feel he is in a position to spurn a fuel duty rise, if he ever was.

Yet he would be a brave chancellor to do it. As the saying goes, there are only two things certain in life: death and the Treasury retreating from unpopular taxes.

• Jack Kessler is a freelance journalist and former Treasury official