From today (30 June), the UK £20 note with the portrait of Sir Edward Elgar on the back of it will no longer be legal tender. The English composer of 'Land of Hope and Glory' has had to make way for the father of economic science and author of The Wealth of Nations, Adam Smith.

Some culture vultures complain that the arts are no longer represented on UK banknotes, but Smith well deserves his place on the currency. He didn't invent economics, of course, any more than Sir Christopher Wren invented churches: but like Wren, he made his material into something fresh, exciting, elegant and imposing. Before Smith, trade and commerce were seen as sordid and demeaning. Only the sellers were seen to gain from it, which is why countries all over the world blocked imports and subsidised their domestic industries. Smith showed that free exchange benefits both sides – people wouldn't do it if they didn't – and that a worldwide network of free exchange would automatically steer resources to where they were most valued, as if an Invisible Hand had directed it. It was self-interested commerce, not governments, that made us free and prosperous. And it was the division of labour that made commerce so productive.

Smith's ideas energised all of the most dynamic minds of that extraordinary age: William Pitt in Britain and Alexander Hamilton in America both read and owned personal copies of The Wealth of Nations. Through his influence, taxes were simplified, tariffs cut, and free trade facilitated. It led to an extraordinary growth of prosperity that benefited the poor more than any – something Smith would have been delighted to see.

You cannot list the greatest thinkers of all time – Copernicus, Newton, Darwin – without mentioning Smith. Yes, Elgar wrote uplifting English music. But Adam Smith uplifted the condition of all humanity.

Dr Eamonn Butler is author of Adam Smith – A Primer.