It started gently. Then it was a tidal wave. Everyone in the lecture theatre was laughing. I continued determinedly to draw a graph of the statistical pattern of happiness over the lifespan. Yet my South African conference audience simply howled. This was no way to treat an earnest international scholar in a tie, I thought. I like my lectures to be humorous - in the right places - but this was ridiculous.
Suddenly my stomach turned wobbly and even I had to grin. My hand was not holding a piece of coloured chalk. Oh no. I am an economist so get me out of here.
For 20 seconds I had been drawing on the board using a pink sweet … a chunky piece of rock candy. Nobody had warned me that this grand, banked lecture theatre near Johannesburg had coloured sweets where the blinking chalk should be. John Cleese would have been proud of me. I ought to have been charging entrance fees.
South Africa, though, was riveting. One of the lovely things about visiting another country is that you do not know the norms. Of course that is, chalk dust aside, an advantage. You can notice things that insiders do not always see.
Of the many nations I have visited, South Africa is probably the most remarkable. Although Virgin Airlines gave me a strange ride home, in a seat with a new entertainment system fitted into a black metal box in the space that actually should have been for the two long bits of me that extend below my torso, and in a plane piloted by an unnervingly avuncular Englishman who told us to call him Johnny Broadsword, I sat thinking that Britain has things to learn from this part of the world.
First, I was fascinated, and at the same time saddened, to find a country with a 40% unemployment rate. Officially I was in South Africa to talk about research into burnout and work-life balance. But when I arrived at the Department of Labour in Pretoria I discovered that, understandably, they were more interested in the problem of high joblessness and low wage levels. What struck me was the way that workers lived many miles from the jobs. Yet there were essentially no buses to bring workers to the work. The quality of a transport system really matters for a labour market's efficiency, I realised, and I reckon that Britain too forgets this. As I sat in a 7am traffic jam in the low sun of Johannesburg's suburbs, the attractions of proper road-pricing were strong.
Second, I found a humility that in my view other nations could learn from. I met extraordinarily mature and warm human beings. One thing about life is that trauma seems to improve people; it makes folk nicer. Perhaps the same goes for countries. The people I met were impressive, and deeply aware of the need for tolerance and equity.
Third, I came upon the most extraordinary art by young black painters and sculptors who can now exhibit out of the shadows. A whirl of stunning colours and sleep-disturbing images, it made me lose my breath. The third lesson I thought about on the flight home was that one cost of unkindness and discrimination is the talent that it throws away.
Fourth, after seeing uncountable middle-class houses with electric fences around them, I found it easy to think that Britain, in its different way, needs for the future to ponder the downside of income inequality.
Finally, I liked the national pride that burst out of South Africans.
Once I protested against this nation. Now I take my hat off to it.