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c.1748 Thomas Delaval began to manufacture copperas at Hartley
1764 family disagreements allowed Thomas to take over responsibility for the Hartley enterprises from his brother John but the businesses got into trouble.
1771 His older brother John Hussey Delaval resumed control of the businesses.
1771 By an Act of Parliament, power was given to Sir Francis Blake Delaval to grant to Sir John Hussey Delaval, in fee simple, all the copperas works - which gives some idea of the importance then attached to this process.