Well I looked up Andrews' Liver Salts and they are partly laxatives and partly for stomach upset, so the consequences of eating the cake may not have been pleasant.

From Wiki: "Andrews Liver Salts was a laxative and antacid for mild stomach complaints. It was sold as a powder which is added to water and mixed, creating effervescence, before being swallowed. The powder contains sugar; an antacid, sodium bicarbonate; citric acid; and a laxative, magnesium sulphate."