During Longueville’s minority his education was entrusted to his mother and her Talbot relatives, and in the winter of 1706–7 his distant cousin Charles Talbot, duke of Shrewsbury, undertook to find a suitable tutor for the young viscount on his forthcoming grand tour.
Longueville returned to England at some point before February 1712, when he was reported as being present at a meeting hosted by Charles Montagu, Baron (later earl of) Halifax, at which were also Robert Harley, earl of Oxford (with whom he was already acquainted), William Henry Bentinck, 2nd earl (later duke) of Portland, Charles Seymour, 6th duke of Somerset, Daniel Finch, 2nd earl of Nottingham, Henry Grey, duke of Kent, Hugh Cholmondeley, earl of Cholmondeley, and Heneage Finch, Baron Guernsey (later earl of Aylesford).
In October 1713 Longueville appears to have rejected Shrewsbury’s offer of his interest to acquire him a position at court.
Longueville took his seat shortly after the opening of the new session on 3 Aug. 1714 and sat for a little over half of the brief final session of the reign of Queen Anne. He attended one day in September and was then active following the dissolution in the elections for Northamptonshire in the Whig interest. Having been encouraged to stand ‘for the sake of preserving peace and good neighbourhood’, the Tory Sir Justinian Isham‡ appealed to his son to wait on Longueville and other of the county’s peers to seek their support, but he bemoaned Longueville’s ‘betrayal’ when it became apparent that the latter intended to employ his interest on behalf of Isham’s opponent. Isham reassured himself that Longueville’s influence in the county was small and his confidence was proved well founded by his re-election.
Longueville returned to the House on 17 Mar. 1715 for George I’s opening Parliament. He prospered under the new regime. In 1715 he was appointed master of the horse to the princess of Wales and two years later he was promoted in the peerage as earl of Sussex.
Sussex married in 1726 but the marriage, reportedly an extremely happy one, was brief; Lady Sussex died in childbirth in 1730. Although still described as being ‘well’ in November of that year, Sussex’s own health deteriorated soon after and he died at Bath in October 1731 aged 41, ‘a martyr to … the unfashionable love of his wife’.
