Last week, I spent some days on a demolition site. In my role as “professional engineer”, I had the arduous task of watching trucks drive by, then writing down their number plates and arrival time.

Sometimes, an hour would go by without excitement. Naturally, I decided to use the time to work out a budget for my life. I pulled out my pen and paper and carefully scribed down my income and expenditure per week. I worked out my monthly and annual costs and divided them by 4 and 52 as was appropriate.

I did long division.

(Later on, I recalled that my fancy mobile phone also has a calculator for times such as these, when you want to work out your net worth on the run.)

“Hey, what are you doing?” The foreman peered curiously at my scribblings.

“I’m making a budget,” I replied helpfully. “I want to work out how much money I can save every week.”

He began reading my list. “Food, board, transport, holidays, opera… Opera?“

“Yeah. Of course,” I said. “Opera costs money, you know.”