Time was when someone doing a quick bit of arithmetic that was beyond their mental ability would do the calculation on ‘the back of a fag packet’.

Of course, in these healthier and more politically correct times any association with the devil’s weed is frowned upon.

I guess it’s for that reason that Gordon Brown has accused George Osborne of carrying out a ‘back-of-an-envelope’ calculation when working out how he was going to fund his £6 billion NIC savings.

This in turn begs the question of who actually writes to anyone nowadays; let alone finds an envelope, buys a stamp, puts the letter behind the clock on the mantelpiece, forgets about it for five weeks, finds it, drops it in the mud while walking across the park, and finally posts it.

Oh yes, I almost forgot, our friends at HMRC – although presumably without the clock and the mud; no comment on the five weeks delay though.

Perhaps George used that brown A5-sized envelope that the department uses to post out your notice to complete a tax return (form SA316 I think) – anyway, I got mine yesterday.

And like George, I was also thinking what I could use that paper for, although I must admit that performing Treasury tax calculations wasn’t actually the first thing that came to mind.

• Blog