Although he was rarely in London, Edward I undertook an expensive remodelling of the Tower, costing £21,000 between 1275 and 1285, over double that spent on the castle during the whole of Henry III's reign. Edward I was a seasoned castle builder, and used his experience of siege warfare during the crusades to bring innovations to castle building. His programme of castle building in Wales heralded the introduction of the widespread use of arrowslits in castle walls across Europe, drawing on Eastern influences. At the Tower of London, Edward filled in the moat dug by Henry III and built a new curtain wall along its line, creating a new enclosure. A new moat was created in front of the new curtain wall. The western part of Henry III's curtain wall was rebuilt, with Beauchamp Tower replacing the castle's old gatehouse. A new entrance was created, with elaborate defences including two gatehouses and a barbican. In an effort to make the castle self-sufficient, Edward I also added two watermills. Six hundred Jews were imprisoned in the Tower of London in 1278, charged with coin clipping. Persecution of the country's Jewish population under Edward began in 1276 and culminated in 1290 when he issued the Edict of Expulsion, forcing the Jews out of the country. In 1279, the country's numerous mints were unified under a single system whereby control was centralised to the mint within the Tower of London, while mints outside of London were reduced, with only a few local and episcopal mints continuing to operate.