At the start of John's reign there was a sudden change in prices, as bad harvests and high demand for food resulted in much higher prices for grain and animals. This inflationary pressure was to continue for the rest of the 13th century and had long-term economic consequences for England. The resulting social pressures were complicated by bursts of deflation that resulted from John's military campaigns. It was usual at the time for the king to collect taxes in silver, which was then re-minted into new coins; these coins would then be put in barrels and sent to royal castles around the country, to be used to hire mercenaries or to meet other costs. At those times when John was preparing for campaigns in Normandy, for example, huge quantities of silver had to be withdrawn from the economy and stored for months, which unintentionally resulted in periods during which silver coins were simply hard to come by, commercial credit difficult to acquire and deflationary pressure placed on the economy. The result was political unrest across the country. John attempted to address some of the problems with the English currency in 1204 and 1205 by carrying out a radical overhaul of the coinage, improving its quality and consistency.