When I helped set up the Social Metrics Commission in 2016, my enthusiasm was born of weariness and frustration. Too many meetings spent debating how to measure poverty instead of how to reduce it. Too many interviews in which arguing over what poverty was crowded out discussion of how to free people from it. Baroness Philippa Stroud (chair of the commission and former adviser to the secretary of state for work and pensions, Iain Duncan Smith) started the commission after seven bruising years in the white heat of government, having those same arguments but with much higher stakes.

Stroud and Duncan Smith had come into government with a grand plan: to sweep away seven old benefits and replace them with universal credit. They worked alongside the Conservative peer, David Freud, who had previously advised the Labour government and then joined the Conservative-led Coalition government in 2010. In his book, Clashing Agendas: Inside the Welfare Trap, Freud tells the gory story of his years in office. He details their battles with the Treasury through the Coalition years and then under the Conservative majority government from 2015.

The original plan for universal credit had widespread support among the policy and research community. It would have increased the generosity of the benefit system at the same time as making its structure simpler and more flexible. Sadly, this approach was dead on arrival at the Treasury. Chancellor George Osborne's grand plan for the UK's social security system was to suck billions of pounds out of it. He had no interest in Duncan Smith's vision until he realized it could be a Trojan horse to slash levels of support.

A backbench rebellion among Conservative MPs prevented Osborne and Prime Minister David Cameron from enormous tax credit cuts in 2015. MPs lost their nerve at the thought of constituency surgeries full of angry people who had seen their incomes slashed by thousands of pounds overnight.