My on-call experience started by accident in the mid-2000s. It was 5pm on the Friday at the end of my first week of employment as a software engineer at a financial services company in London. I was in the process of closing down my IDE for the weekend when my boss sauntered up to my desk, grinning awkwardly. He was carrying an IBM Thinkpad, a Blackberry, and the unmistakable burden of a man who needed to call in a favour.