Trenchard, John (1668/1669–1723), political pamphleteer and member of the Irish forfeitures commission, was the only son among four children of William Trenchard, of Cutteridge in Wiltshire, and his wife, Ellen, daughter of Sir George Norton of Abbots Leigh in Somerset. He was admitted to TCD on 29 May 1685, aged sixteen, and attended the Inner Temple in London, being called to the English bar in 1689. If he ever practised law it was not to earn his living, for he was the heir to great wealth, though the claim that he lent the invading Prince William of Orange (qv) £60,000 seems dubious.
Trenchard made his name in a pamphlet war over the question of a standing army, which erupted in England in 1697 in the aftermath of the peace of Ryswick. The extreme whig position, of which Trenchard was the prime advocate, was that in peacetime anything more than a token permanent army was a threat to English liberties. The controversy, which brought William III to the brink of abdication, was largely an aspect of English domestic politics but had Irish dimensions. The account by Robert Molesworth (qv) of arbitrary power in Denmark had helped set the tone of the debate, to which another Irishman, John Toland (qv), was a contributor. Furthermore, there was a well-founded whig apprehension that the apparent size of the English standing army might be reduced by putting forces on the Irish establishment, while a list of the Irish forces of King James (qv) in exile in France, published by Trenchard's opponents as an argument in favour of a standing army, also helped raise the temperature of the debate.
The English house of commons subsequently turned its attention to the other great whig grievance against the king, namely the management, and granting away to royal favourites, of Irish lands forfeited by Jacobites. The result was an act of the English parliament of 1699 establishing a commission of inquiry into the forfeitures, whose seven members included Trenchard. He did not disappoint those who intended that his presence on the commission would ensure a report embarrassing to the king. The commission split on the delicate question of whether it ought to include in its report a huge grant made to Elizabeth Villiers, a former mistress of the king. Trenchard argued with vehemence that it should, and the grant was included in the report signed by the majority, which was in general extremely critical of mismanagement of the forfeitures and over-optimistic about the prospect of raising money for public uses through their sale.
The report led to a further English act, in 1700, for resuming the grants, and selling the lands. Trenchard was appointed to a new commission of thirteen trustees to implement this Act of Resumption. The commissioners, paid £1,500 a year, sat from 1700 until 1703 in Chichester House, in Dublin, the building used by the Irish parliament when in session. The titles to the lands in question were often very complex and disputed, and the adjudications of the commission left many dissatisfied, while the entire episode was seen by many Irish protestants as a heavy-handed intervention, motivated by domestic English political concerns. Trenchard was one of just two men (the other being Francis Annesley (qv)) who sat continuously on the two commissions and, while no single figure dominated this exercise of English parliamentary power in Ireland, he may justly be seen as the embodiment of its moving spirit.
He retired to private life until 1720, when he took up journalism: he wrote in the Independent Whig, which attacked the high-church party of the Church of England, and in the London Journal, which published ‘Cato's letters’ and which subsequently became a government organ. He was returned to the English house of commons for Somerset in 1722. He was married twice. His first wife was Anne, daughter of Sir Thomas Scawen; she died by suicide in 1718. He married secondly, in 1719, Anne, daughter of Sir William Blackett. There were no children of either marriage. He died 16 December 1723.