And of course they will be, by force of circumstance or otherwise. Herb Stein, Richard Nixon’s economic adviser, once remarked: “If something cannot go on for ever, it will stop.” In fact, it is quite unlikely that public debt in the UK will ever reach the levels projected by the OBR, if only because the markets won’t allow it. The trick is to achieve fiscal sustainability in a planned way, rather than wait for a crisis to deliver it by externally imposed diktat, in the manner of the eurozone periphery.