In Britain a poor household is officially defined as one with an income less than 60 per cent of the median. A law passed by the last government declares an unattainable target of reducing the proportion of children who live in poor households to below 10 per cent by 2020.

No surprise, therefore, that in today’s austere circumstances Iain Duncan Smith, the UK’s work and pensions secretary, has attempted to start a debate about the definition of poverty. But his motives are not entirely cynical: Mr Duncan Smith has a record of real social concern.

People who struggle to find enough food to eat are poor. The World Bank’s poverty line is an income of less than $1.25 a day. Financial Times readers, who spend more than that amount on their morning newspaper, are in no position to dispute that judgment. In the past two decades, economic growth in China and India has reduced global poverty by an unprecedented amount. That achievement is not diminished because some individuals in both these countries have become very rich. Fundamentally, poverty is about absolute deprivation.