The Bath bun is a sweet roll made from a milk-based yeast dough with crushed sugar sprinkled on top after baking. Variations in ingredients include enclosing a lump of sugar in the bun or adding candied fruit peel, currants, raisins or sultanas. The change from a light, shaped bun to a heavier, often fruited or highly sugared irregular one may date from the Great Exhibition of 1851 when almost a million were produced and consumed in five and a half months (the "London Bath bun").