Early gunpowder weapons were introduced to England from the 1320s onwards and began to appear in Scotland by the 1330s. By the 1340s the English Crown was regularly spending money on them and the new technology began to be installed in English castles by the 1360s and 1370s, and in Scottish castles by the 1380s. Cannons were made in various sizes, from smaller hand cannons to larger guns firing stone balls of up to . Medium-sized weapons weighing around 20 kg each were more useful for the defence of castles, although Richard II eventually established 600 pound (272 kilo) guns at the Tower of London and the 15,366 pound (6,970 kilo) heavy Mons Meg bombard was installed at Edinburgh Castle.