Frank Field MP (pictured) has been asked by the Prime Minister to look into poverty. He's a good choice for a daunting task, made no easier by the redefinition of poverty in relative terms.

In The Daily Telegraph, Mr Field criticises the last Government for setting a target of abolishing child poverty by 2020. It wasn’t achievable, he says. Maybe - but it wasn’t, as he goes on to say, mathematically impossible.

“Any candidate sitting GCSE maths should be able to explain that raising everybody above a set percentage of median income is rather like asking a cat to catch its own tail” he writes. “As families are raised above the target level of income, the median point itself rises”. Not so.

Had he said the mean rather than the median, he would have been right. But it’s perfectly possible to raise the poor a notch or two without shifting the median. Imagine an economy of nine people with earnings of 1, 2, 3 and so on, to 9.  Median income is 5 - the midpoint when ranked. Raise the income of the people earning 1 and 2 to 3 (60 per cent of median) and "poverty" so defined is eradicated. The median hasn’t changed: there are still as many people earning less than 5 as there are earning more.

Doesn’t mean it’s possible, mind.