I would have thought that, having decided to invest X amount of money per unit time, what matters for beating inflation is the interest you can get on it, not the size of X. Sixpence will fail as savings because it’s 0.021% of your annual income, not because of inflation; even if you assumed the value of money was perfectly stable, it would take you a long time to build up any sort of reserve at that speed.
I would have thought that, having decided to invest X amount of money per unit time, what matters for beating inflation is the interest you can get on it, not the size of X. Sixpence will fail as savings because it’s 0.021% of your annual income, not because of inflation; even if you assumed the value of money was perfectly stable, it would take you a long time to build up any sort of reserve at that speed.