Corn laws, 1794-1846, set duties on grain imports into Britain to protect British agriculture from outside competition. (In Britain, "corn" is the name for CEREAL CROPS. ) By the 1820s, increased food demands in Britain led to revisions giving preference (lower duties) to colonial over foreign imports, thereby promoting an imperial grain supply. Preferential rates offset the costs of transatlantic transport for British North American grain and built up a major colonial stake in wheat exporting. Shifts in the level of duties primarily to suit British harvests and prices could still trouble this commerce; yet in general it rose steadily, particularly after the CANADA CORN ACT was passed in 1843. Then in 1846 Britain repealed the Corn laws as part of a movement towards free trade. The consequent loss of preferential duties seemed a hard blow to the Canadian grain trade; but it recovered in the prosperous 1850s. Moreover, the lifting of imperial economic controls also brought relief from political controls, and thus imperial recognition of RESPONSIBLE GOVERNMENT in British North America.