The later 18th century saw a revival when the Fens began to be effectively drained. The Act of Parliament permitting the embanking and straightening of the fenland Witham was dated 1762. A sluice, called for in the act, was designed to help scour out The Haven. The land proved to be fertile, and Boston began exporting cereals to London. In 1774, the first financial bank was opened, and in 1776, an act of Parliament allowed watchmen to begin patrolling the streets at night.