The complexity of large or at least substantial estates ensured that stewards could never be mere rent collectors, negotiators of leases and seekers of tenants because their masters' estates yielded more forms of income than those which derived from tenancies and leases. Many of these other sources of income required the supervision of a man with a keen nose for business, capable of handling substantial business transactions which were often complex and demanding. Occasionally one encounters stewards, like William Gilpin at Whitehaven, who were quick to perceive potential assets and eager to exploit them on their master's behalf. In brief, some estates were well served when they were placed in the charge of a man of enterprise, a man with entrepreneurial skills. This type of steward was needed on a greater proportion of estates than might be supposed. The industrial emphasis which Sir John Lowther's coalmines gave to his estate at St Bees-Whitehaven was certainly unusual, but it was not unusual for some estate income to derive from mining royalties in regions which were rich in coal, lead, tin or copper, or for some income to derive from quarries for slate, stone and millstones.