Jocelyn sat for the family borough of Dundalk in the last Irish parliament and supported the Union, whereupon he resigned his seat to suit his father. After an application to the chief secretary on 1 Oct. 1802 for an exchange, he was placed on the customs board in 1803.
Jocelyn was at first prevented by a severe rheumatic complaint from attending Parliament, but he was in London supporting government in the spring of 1808 when Roden, fearful of a change of ministry, tried to nail the Irish government down on its promise to reinstate Jocelyn. They offered to do so ‘tomorrow’ if he vacated his seat, but declined to admit a substitute for him unless of acknowledged fitness, or to allow any more precise engagement than an honourable agreement. They advised Roden to bide his time. The viceroy then pacified him by assuring him that ‘if I should be removed I will either appoint his brother or his friend if a proper person’.
