It's one of those -illions moments, where everything steps up in magnitude. I remember when government budgets, tax receipts, public expenditure, public borrowing and the rest was always expressed in millions, or hundreds of millions. Sometime in the 1980s, the numbers started to go through the 1,000 million ceiling, and than we had to choose – should we stick with expressing them in thousands of millions, or should we adopt the American rule of calling 1,000 million a billion? Eventually The Economist decided it for us, and we opted for billions.

And now, with bank bailouts and gargantuan, mistaken, Keynesian New Deal spending programmes, we're into trillions. In just 25 years, government financial measure have grown not just once or twice or even ten times, but a thousand thousand times.

But how do you write trillion? When budgets were just in the millions, we'd write £1m. When they reached the billions, we could have written £1b, but for clarity £1bn has become the norm. That use of two letters seems appropriate. A billion is bigger, after all.

So how do we write trillion? We could to £1t or £1tr, but I would favour, once again, something a bit longer, to match the scale of the figure - £1trn.

Dr Eamonn Butler's new book, The Rotten State of Britain, is published later this month.