Preston, Robert (d. 1503), 1st Viscount Gormanston , administrator, was the son of Christopher Preston, 3rd Lord Gormanston. He came of age about 1450, when he entered into his considerable inheritance, centred on Gormanston in Meath. He married Jenet, daughter of Sir Richard Molyneux of Sefton, New Liverpool, with whom he had two sons and two daughters. His first position of note in the English government in Ireland was as deputy chancellor from 1461. Although he had close connections to William Sherwood (qv), bishop of Meath, who was opposed to the power of Thomas FitzGerald (qv) (d. 1478), 7th earl of Kildare, Gormanston sided with Kildare in his fervent commitment to the protection of the Pale from the Irish: he was one of thirteen inducted into the Fraternity of St George in 1472, a standing force established by Kildare (who was then justiciar of Ireland) to defend the Pale.
Gormanston's relations with the house of Kildare, always somewhat strained, worsened during 1478, after the death of the 7th earl on 25 March and the election of his son Gerald FitzGerald (qv) (d. 1513), the 8th earl of Kildare, to take his place as justiciar. This nepotistic succession troubled Edward IV, who reversed the election, making George (d. 1478), duke of Clarence, lord lieutenant, and in July dispatching Lord Henry Grey (d. 1478) to Ireland as Clarence's deputy. Kildare, reluctant to relinquish his office, vigorously opposed Grey's appointment and held a parliament between May and September that extended government control over the Ormond earldom through an act of resumption. In response Grey cultivated support among those English nobles of Ireland who were opposed to Kildare, including Gormanston, who was created 1st Viscount Gormanston on 7 August 1478 for his ‘probity, knowledge, loyalty and industry’. In the teeth of Kildare's opposition Grey managed to hold a parliament in November 1478 at Trim, but, exasperated by the earl's resistance, he embarked for England early in the new year, prevailing upon Gormanston to take over his office. In May 1479 the four-year-old Richard, duke of York, succeeded his brother Clarence as lord lieutenant, with the result that Gormanston continued as deputy in Ireland. To bolster his position he was granted forty archers and twenty men at arms to serve with him between 1 June and 30 September 1479. He was still acting as deputy in Ireland on 18 October, but his tenure ended shortly afterwards when Kildare returned triumphant from a visit to London with the king's grant of the appointment of lord deputy.
Thereafter Gormanston fell in behind Kildare and lent his support to the earl as champion of the cause of Lambert Simnel (qv) (d. 1534) against Henry VII in 1487; he received a pardon on 25 May 1488 for his activities. In 1489, with Kildare and the rest of the temporal lords of Ireland, Gormanston was summoned to Greenwich, where the king humiliated them by having Simnel serve them at a banquet. Even though Kildare again returned to Ireland as deputy lieutenant, Henry did not trust him, and he was replaced on 11 June 1492 by Archbishop Walter FitzSimons (qv) (d. 1511), while Sir James Butler (qv) of Ormond (d. 1497) became treasurer. This led to a fierce struggle between Kildare and Butler, which the king could not allow to continue. In September 1493 Archbishop FitzSimons resigned his position as deputy lieutenant to Gormanston, who promptly held a council at Trim on 12 September devoted to security matters. It was attended by Kildare and most of the Pale magnates, along with the king's commissioners, who were ordered to deliver their pledges to the royal castles at Dublin and Trim. Gormanston held a parliament in late October at Drogheda, but its proceedings were declared void as the duke of Bedford had resigned his commission as lord lieutenant of Ireland just before it was held.
Gormanston was included along with Kildare and Sir James Butler in the group summoned to England by the king for prolonged discussions in 1493–4. During that period his son, William Preston (qv), acted as his deputy. Gormanston seems to have continued in office as deputy lieutenant until the arrival of Sir Edward Poynings (qv) in October 1494. Thereafter he appears to have retired to his Meath estates, where he died 9 April 1503.