Why are the Tories split on universal credit?

<div>The Commons will today see a debate over extending the universal credit uplift. While Thérèse Coffey, the work and pensions secretary, wants the weekly increase to remain, Rishi Sunak wants to replace it with a one-off £500 payment. Isabel Hardman talks to James Forsyth and Katy Balls about the Tory split.</div>