This is the third and final part of this series where I examine claims made by senior advisors to the British Labour Party that a fiscal policy that is designed using the insights provided by Modern Monetary Theory (MMT) would be “catastrophic” and render the British pound worthless. In Part 1, I examined the misunderstanding as to what MMT actually is. A senior Labour advisor had claimed, in fact, that any application of MMT would be “catastrophic” for Britain. He talked about MMT “policy prescriptions”, which disclosed an ignorance about the nature of MMT. In Part 2, I considered the British Labour Party’s Fiscal Credibility Rule and demonstrated that its roots were in core neoliberal ideology and any strict adherence to it would not be consistent with progressive outcomes. I noted that it was likely to promote a private ‘debt-bias’ that was unsustainable. In this final part, I explore some economic history over the last five decades to give some further force to the argument presented in Part 2. And I finish by arguing that a well governed, rule of law abiding Britain with a government building and maintaining first-class infrastructure, with excellent public services (energy, transport, health, education, training, environmental certainty, etc), with a highly skilled labour force, and regulative certainty, would be a magnet for profit-seeking private investment irrespective of whether it was running a continuous fiscal deficit or not. Yet, it is highly likely, given Britain’s history, that such a deficit (both on current and capital contexts) would be required.