Iain Duncan Smith spent five years in the Cabinet not resigning over cuts to disabled people's payments that did happen, before resigning over that one that won't happen. The proposed cuts to the Personal Independence Payment had already been called off following a public revolt by Conservative backbenchers, and news that the cut will be cancelled arrived in journalists' inboxes long before Duncan Smith's resignation did.

All of which might lead you to think that something else is going on, that this resignation has more to do with the coming referendum on Britain's membership of the European Union than anything to do with the welfare budget. For politicos - weaned on a diet of The West Wing, Borgen, Scandal et al - this is a particularly tempting narrative. We love to believe that there's a plan, that everything happens for a reason. There's just one small problem here: and that problem is Iain Duncan Smith.

As exciting as it would be for people like me, Iain Duncan Smith simply isn't clever enough to have thought this many moves ahead. This is the man who is the chief architect of the universal credit, which was supposed to have been rolled out in October 2013, and in March 2016 has been rolled out to the grand total of 203,000 people - and by "people", I mean "single men without dependents", the only group whose claims are simple enough to be processed on the universal credit.

This is the Secretary of State who has wasted so much money on failed policies that the government is able to claim - entirely truthfully - that the money being spent on disabled people has gone up, even though not a single penny has gone to disabled people while countless billions have been lavished on IT systems that don't work and a benefit reform that will never be implemented.

This is the man who as leader of the Conservative party mistook a spoof poster - "It rains less under a Conservative government" - for the real thing, happily posing underneath it. This is the man who Osborne described as "not clever enough" after watching him present on his welfare reforms in the last government. This is the man who, despite having been the longest-serving Secretary of State at the Department for Welfare and Pensions, leaves it having implemented nothing and done nothing.

It is certainly true that this is a man who has been waiting for an excuse to walk out of the government since the Autumn Statement in November 2015, when Osborne moved the tax credit cuts into the universal credit rollout - a sign that, as far as the Treasury was concerned, the universal credit will never happen. As civil servants in the DWP have observed, Duncan Smith has been a broken figure since that setback, one that would have been obvious if he had had any grip on his department.

Resigning as part of a plan? As exciting as that would be, Iain Duncan Smith simply isn't good enough for that.