The point is that it's not a matter of opinion, it's basic maths. If I raise 20 billion from a particular tax, for example, and I decide to abolish the tax, then I know that it's going to cost me 20 billion. Now there can be a bit of uncertainty about the exact amounts, because these things fluctuate year-to-year, but generally speaking, you know how much a policy will cost. And that's why credible parties explain how they are going to pay for things, and populist parties don't even both addressing it because they clearly haven't done the maths and don't care to do it, because it would show their plans are untenable. Diane Abbott was crucified for not knowing the cost of extra police officers in a TV interview. Reform are Diane Abbott on crack.