Egerton’s family were extremely wealthy Cheshire landowners, whose association with the Tatton estate went back to 1598. His grandfather and namesake William Tatton Egerton (1749-1806) had sat for the county, 1802-6, and his father Wilbraham Egerton, 1806-31; but before Egerton assumed the same role he was returned for Lymington at the 1830 general election, as the nominee of its Tory patron Sir Harry Neale*. He was listed by the Wellington ministry as one of their ‘friends’ and voted in their minority in the crucial division on the civil list, 15 Nov. 1830. His application for a month’s leave, made through his father, 23 Nov., was challenged by Hume, who withdrew his opposition on being informed that Egerton was to be married. His wife, recalled her kinswoman Lady St. Helier, was an ‘extraordinary woman’, who ‘said out loud everything she thought’, but ‘was not a person who had many friends, because people were afraid of her and what she might say’.
At the 1832 general election he successfully stood as ‘a thorough going Tory’ for Cheshire North, where he sat for the next 26 years. Raised to the peerage by the second Derby ministry, he continued to act with the Conservatives in the Lords.
