[1]: 251 In February 1575, he was tasked with a mission to the Elector Palatine to convince him to send an army into France to aid the Huguenots under the Prince de Condé.
Examples are the salt monopoly for the English east coast he received in 1585[4] and the lease of Downton rectory, that he eventually sold on to the Raleigh family.
He was to assure king Philip II of Spain of Elizabeth's good intentions and to convince him that the new governor-general in the Habsburg Netherlands, Don Juan would best be recalled.
On the return voyage he visited both Don Juan and the Prince of Orange in the Netherlands to receive their respective views and report back to Elizabeth.
[1]: 252 In 1579, an arrangement was made for a six-monthly rotation of the clerks of the Privy Council, Wilkes' turns being May–August and November–December, but he was available for special commissions during the remainder of the year.
In 1581 for instance, he engaged in the interrogation under torture of the Jesuit priest Edmund Campion in this context, and in 1583 he investigated the conspiracy of Arden, Somerville, and Hall.
Wilkes maintained a secret correspondence with the Queen's Secretary of State and spymaster, Sir Francis Walsingham, in which Leicester was known as Themistocles, that grew increasingly critical of the policies of the Earl.
In his capacity as a member of the Council, he addressed the States of Holland with a "Remonstrance" in which he defended the policy of the Earl to oppose the Regenten and promote the democratic (and extreme Calvinist) factions with an appeal to popular sovereignty "by default of a legal Prince."
This prompted the States to a response, written by François Vranck, that would become an important ideological statement of the principles of the (largely unwritten) "constitution" of the Dutch Republic.
[1]: 253 Besides the Remonstrance referred to above, Wilkes left A Briefe and Summary Tractate shewing what appertaineth to the Place, Dignity, and Office of a councilor of estate in a Monarchy or other Commonwealth, dedicated to Sir Robert Cecil, as a work of political philosophy.