From 1790 to 1794, Wickham was a commissioner of bankrupts. Following the passing of the Middlesex Justices Act of 1792, Wickham was appointed in 1793 as one of the new stipendiary magistrates. In this position he began to undertake secret work for the Government, at the behest of Lord Grenville, the then Foreign Secretary. This was at a time when the French Revolution was causing great concern to the British political establishment, and powers were given to magistrates under the 1793 Aliens Act. An early action of Wickham's in his new post was the infiltration of the radical London Corresponding Society, leading to the arrest and trial for treason of its leaders. Despite the apparent failure of his spies to uncover anything incriminating amidst the society's meetings and papers or to entrap the members in sedition, treason, or other crimes, Wickham was made 'superintendent of aliens' in 1794 by the then Home Secretary, the Duke of Portland.
Intelligence activities
Because of his knowledge of Switzerland, Grenville sent Wickham to that country in 1794 as assistant to the British ambassador. A year later he was named chargé d'affaires when the ambassador took extended leave, and then appointed ambassador in his own right. His unofficial duties were to liaise with French opponents of the Revolution. By 1795, England was openly combating the French revolutionaries who had usurped and beheaded King Louis XVI and his Queen, Marie Antoinette. Wickham established a spy network in Switzerland, southern Germany and in France and negotiated with French Royalists and others, supporting amongst other initiatives the disastrous rising in la Vendée. Wickham strengthened the British intelligence system by emphasising the centrality of the intelligence cycle - query, collection, collation, analysis and dissemination - and the need for an all-source centre of intelligence. The government secretly funded Wickham with a substantial budget for his objects. A good deal of this was spent in a complex plot to bring French revolutionary general Charles Pichegru, over to the ranks of Louis Joseph, Prince of Condé who maintained an army on the Rhine. Wickham advanced £8,000 to feed and supply Pichegru's troops; however, Pichegru vacillated and the initiative failed. Wickham also reported on French troop positions, armaments and operations. French spies, however, learned of his network, and France pressured Swiss authorities to expel him. Wickham resigned, returning to England in 1798, where he resumed, after some internal wrangling, his position as Superintendent of Aliens, and was appointed Under-Secretary of State for the Home Department. For a year and a half he was " the effective head of the secret service". He returned to Europe to Swabia, close to the Swiss border, in 1799 where his averred role was to liaise with the armies of Austria and Russia in Europe, which were supported by Britain against Napoleon. Again he negotiated inconclusively with Pichegru, but his expensive intrigues were rendered useless by Napoleon's victory at the Battle of Marengo ; moreover he was accused in London of misuse of public funds, which brought him close to a nervous breakdown. He returned to London in 1801.
Ireland
In 1802 Wickham was appointed to the Privy Council and named Chief Secretary for Ireland, a post he held until 1804, when he resigned following the execution of Robert Emmet, as he felt the laws governing Ireland to be "unjust, oppressive and unchristian". He also entered Parliament as MP for the Irish borough constituency of Cashel: he sat for Cashel from 1802 to 1806, and for Callington in Cornwall from 1806 to 1807.
Family papers
The Hampshire Record Office holds a number of Wickham's papers. The archive relates also to his grandson William Wickham, who was vice-chairman on the first County Council. The archive includes grants of full powers to Wickham in 1799 and 1801; also poll books for the election of members of parliament representing Oxford University in 1801 and 1809, a plan showing the arrangement of wine in the cellars, and papers about Wickham's success in growing fig trees, which continue to flourish at his home in Binsted. His other property was Lullebrook Manor at Cookham in Berkshire.
