Tremayne, Edmund (c.1525–1582), government official and adviser on Irish affairs, was the second son of Thomas Tremayne of Collacombe, Devonshire, and Philippa, daughter of Roger Grenville of Stow. In 1553 he entered the service of Edward Courtenay, earl of Devon; the following year he was imprisoned in the Tower of London on suspicion of involvement in the rebellion of Sir Thomas Wyatt (d. 1554). Released on 18 January 1555, he appears to have rejoined Courtenay who was then in exile in Italy. He returned to England following the accession of Queen Elizabeth. He probably joined the household of Francis Russell, earl of Bedford, in Calais in 1557. In 1559 he was MP for Tavistock. At court he attracted the attention of Elizabeth's minister William Cecil, who in 1569 sent him to Ireland.
Tremayne landed at Waterford in early July 1569 and was to remain in Ireland until 1571. He originally intended to serve Sir John Pollard, who had been appointed lord president of Munster, but in the end Pollard never took office. Tremayne then accepted an offer from the lord deputy, Sir Henry Sidney (qv), apparently to act as his private secretary, and served in that capacity from April 1570. During that time Archbishop Adam Loftus (qv) commended him for his good work. By December 1570 he was being considered for the post of clerk of the English privy council, and, following his return to England in late March, he was appointed to that post on 3 May 1571. The following year he was MP for Plymouth. In 1573 he returned briefly to Ireland to discuss the state of the realm with the lord deputy, Sir William Fitzwilliam (qv); he landed at Dublin on 27 June and returned to England apparently a month later. Back in England he returned to his work for the privy council. In September 1576 he was nominated as a possible candidate for the post of vice-treasurer of Ireland, while in July and August 1579 he was involved in the provisioning of troops then being sent to Ireland to counter the outbreak of the Desmond rebellion (1579–83).
Tremayne's importance to the history of Elizabethan Ireland lies in a series of reports he compiled between 1571 and 1575 based on his own observations and on those of Sir Henry Sidney. In these treatises, he argues that the government's support for colonial ventures involving the confiscation of lands held by Irish lords served only to provoke rebellions throughout the country, and that the colonists would inevitably degenerate into barbarity when placed in an uncivilised environment. Instead, the crown should drive a radical and thorough reform of Irish society by assembling a large army and quartering it all over the country. The Irish lords would be compelled to abolish their private armies, which they used to oppress their tenants. In return, the lords would receive a compensatory rent from their tenants proportionate to the extent of the powers they had surrendered. Further, both lords and tenants would be forced to contribute, in cash or in kind, to the maintenance of the royal army. This contribution would make the scheme self-sustaining after an initial period during which the English exchequer would subsidise the Irish government. While curtailing the lords’ power, Tremayne's plan still left them with a strong role in local society and did not threaten their property rights.
Although these proposals were framed as representing an enlightened reform programme that made some concessions to Gaelic society, they actually entailed placing Ireland under military occupation with all the discontent and abuses of authority that such a situation entailed. In particular, the scheme gave far too much power to the notoriously grasping army officers. He acknowledged this problem without providing any practical solutions. Tremayne's plan found a champion in Sidney who was reappointed lord deputy of Ireland in 1575. Indeed, Sidney may well have been the true progenitor of the scheme, which became the centrepiece of his second lord deputyship. Although eventually implemented with some success in Connacht, the plan foundered elsewhere due to a combination of its inherent flaws, the queen's parsimoniousness and Sidney's inability to win the confidence of the Irish nobility.
Tremayne inherited Collacombe and the family estates upon his elder brother's death on 13 March 1572. He married Eulalia, daughter of Sir John St Leger, of Annery, Devon, in September 1576, with whom he had a son, Francis, named after the earl of Bedford, and a daughter. Tremayne made his will on 17 September 1582 and died at Collacombe a few days later. Francis Tremayne outlived his father by only six weeks, whereupon the estates passed to Tremayne's brother Degory.