Liz Truss and Kwasi Kwarteng possess a level of intellectual self-confidence usually found among undergraduates. They always have. Since 2010, when all three of us were first elected as Conservative MPs, they have known what they believe – and have viewed those who didn’t agree with them, or didn’t share their unshakeable certainty, with amiable contempt. The UK is beginning to discover what it is like to be led by people who despise compromise and lack all humility. Every decision they have made in the past few weeks has its roots in the book they published as newly elected MPs, Britannia Unchained. At the time it was viewed by most MPs and commentators as a harmless, if needlessly provocative, attempt by some young thrusters from the Conservative party’s right wing to get noticed. But ideas that survive the editorial process of a political publication can cause serious harm when crudely applied without regard to evidence or context. Having imbibed a simplistic version of Ronald Reagan and Margaret Thatcher’s economic doctrines in their late teens, they have never asked themselves how likely it is that the same recipes will work 30 years later. Policy wonks are often dazzled by the simplicity and clarity of an intellectual theory. I know because, like the prime minister, before entering parliament I was one. But real life and a modern economy do not conform to ideological constructs. The UK is dealing with an unprecedented combination of challenges: an ageing workforce, an energy supply shock caused by a European war, the sudden erection of trade barriers between British businesses and their largest export market, and supply chains that have been upended by a global pandemic. Claiming that cutting taxes on the richest individuals and largest companies will lead to a surge in economic growth betrays a wilful naivety. If you look at the evidence, and evaluate the relative performance of advanced economies over the past 15 years, as the Resolution Foundation’s Economy 2030 inquiry recently did, you discover that low rates of taxation do not automatically produce high rates of growth in productivity, GDP per capita or living standards. What does is sustained and substantial investment by government and businesses in infrastructure and research, the adoption of new technologies and the improvement of workers’ technical skills. The sobering truth is that for most of the past 30 years, government and businesses in the UK have done far too little of any of this. With their obsessive focus on tax rates and deregulation, Truss and Kwarteng seem to have learned nothing from the superior performance of the countries most similar to our own – France, Germany, the Netherlands – in the three decades since their ideological heroes left office. My brief career in politics taught me a few crucial lessons. Those who are full of certainty are usually wrong. The capacity to listen, to observe, to weigh up evidence and to change your mind are some of the most important qualities in a leader. Of all the different kinds of fool, the most dangerous kind is the clever fool. Of course leaders need a strong sense of direction. But it should be formed by principles and values, not economic theory. The policies they pursue should be inspired by those values but rooted in evidence about what actually works and what people want. In the past few days, the values of sterling and government bonds have registered the alarm felt by international investors about the UK’s prospects. But the British economy is resilient and there is a limit to how much permanent damage even these two headstrong ideologues will be able to do. In two years’ time, voters will be given a choice. By then I expect that there will be millions of former Conservative voters who will have tired of being lab rats in Truss’s and Kwarteng’s ideological experiments. They will look for leaders who are prudent, responsible and steady. Who don’t think they know everything. Who listen, and are in touch with people’s everyday concerns. I predict that they will conclude, as I have done, that it is the Labour leader, Keir Starmer, and his shadow chancellor, Rachel Reeves, who best fit the bill.