Darcy, Sir John (c.1280–1347), baron and justiciar of Ireland, was the son of Sir Roger Darcy of Nottinghamshire and Isabel, daughter of Sir William d'Aton of Yorkshire. His early career was closely bound up with Aymer de Valence, earl of Pembroke, whose service he entered in 1307 and with whom he made indentures in 1309 and 1310. From 1317 to 1320 he was constable of Norham castle; in 1319 he was made sheriff of Nottinghamshire and Derbyshire, and he served with Pembroke in Scotland in 1322. Appointed to the politically sensitive post of sheriff of Lancashire in February 1323, he was also one of Valence's retinue sent to negotiate with the Scottish envoys at Newcastle in May that year.
On 18 November 1323, by virtue of his long and loyal service to Pembroke, he was appointed justiciar of Ireland, a position he was initially loath to take up, though he finally landed in Ireland in February 1324. His first task on arriving in the lordship was to ensure Anglo-Irish loyalty to Edward II after the escape from captivity of Roger Mortimer (qv) a year earlier. He oversaw a clean sweep of the administrative and judicial personnel who might have been tainted by connections with the former lieutenant and was made a custodian of some of Mortimer's former lands. At a parliament he called at Dublin in May, the magnates reaffirmed the undertakings made at the Kilkenny parliament of 1310 to restrain and discipline their retainers and kinsmen. The parliament was also concerned with the notorious witch trial of Alice Kyteler (qv), as Darcy tried to mediate between her son, William Outlaw (qv), and the inflammatory bishop of Ossory, Richard Ledrede (qv). He returned to England in July to report his initial achievements and raised some money from the younger Despenser.
When he returned to Ireland he found that his success in the Kytler affair had proved ephemeral, and a dispute in Munster over the Clare inheritance was threatening to develop into internecine war between Maurice fitz Thomas FitzGerald (qv) and Arnold le Poer (qv). When the former stormed Bunratty castle in 1325 Darcy was forced to intervene and a delicate truce of sorts seems to have been cobbled together. After the collapse of the Despenser regime in England late in 1326 Darcy appears to have remained loyal to the deposed king and failed to restore Mortimer's Irish estates and relinquish his constableship of Trim. He was replaced as justiciar on 1 May 1327 by Thomas fitz John FitzGerald (qv), the earl of Kildare, though notification of his removal had been made the previous February.
Darcy's reappointment as justiciar on 19 February 1329 (he took up office in May) was an attempt to halt the disintegrating authority of the Mortimer government in the lordship. To an extent he was successful: at Kilkenny he managed to patch up the differences between the various warring factions. Following the murder of John Bermingham (qv), the earl of Louth, in June, he oversaw the inquisitions into the crime but did little to punish the offenders, no doubt under instructions from Mortimer. The following month he received the custody of some of the earl's lands and also married Joan de Burgh, daughter of the late earl of Ulster, Richard de Burgh (qv), and widow of the earl of Kildare. In 1331, after the death of Joan's eldest son, the 3rd earl of Kildare, he obtained custody of the Kildare inheritance which he held until 1340. In August 1329 he led a successful expedition against the O'Byrnes in Wicklow, and the following year spent much of his time trying to deal with serious disturbances in Mortimer's lands in Meath and negotiating a settlement between William de Burgh (qv), the earl of Ulster, and Maurice fitz Thomas, now earl of Desmond. He was recalled to England on 17 February 1331 and shortly afterwards was made a special envoy to France to negotiate the king's marriage.
He was appointed justiciar of Ireland for the third time on 30 September 1332, a position he retained until 28 July 1337, though much of his time was spent in England. When he took up office on 13 February 1333 he attended to the release of Desmond and also encouraged the rehabilitation of Walter de Bermingham (qv). In September he landed in Ulster with the army he had raised for a campaign in Scotland in order to take revenge for the earl of Ulster's murder. Afterwards he sailed his force to Dumbarton where they supposedly slew some 700 Scots. In 1335 he was again charged with recruiting troops for the Scottish wars and in August he led a sizeable Irish contingent, including the earls of Ormond (qv) and Desmond and Walter Bermingham, which unsuccessfully laid siege to Rothesay castle for more than ten weeks. Between June and July 1336 there was growing concern in England over suspected maladministration in Ireland from which Darcy was not exempted. The justiciar and other ministers were accused of having failed to protect the weak from the depredations of the strong and of being far too close to many of the leading Anglo–Irish magnates.
After leaving the justiciarship, Darcy remained high in Edward III's favour and was made steward of the king's household; thereafter he was employed on a number of occasions as an envoy. He accompanied Edward to Antwerp in 1338 and on 1 March 1340 he obtained the forfeited lands in Ireland of the alien count of Eu; two days later he was granted the justiciarship of Ireland for life, but because of the necessity of his continued personal attendance on the king a number of deputies were appointed in his stead. On 18 February 1344 this grant was redeemed by Edward in return for revenues in fee. Appointed chamberlain of the royal household in 1341, Darcy was present with the king at the battle of Crécy (1346) and was one of those sent to parliament to announce the famous victory. John Darcy of Knaith died 30 May 1347, perhaps at Calais.
His first marriage, to Emmeline, daughter of William Heron of Yorkshire and Alice, daughter of Sir Nicholas Hastings, also of Yorkshire, produced two sons and a daughter. He also had a son and daughter from his second marriage, to Joan: William Darcy went on to form a branch of the family in Ireland and Elizabeth married James Butler (qv), the 2nd earl of Ormond, whose wardship Darcy had been granted in 1346.
Despite relatively modest origins, his service and loyalty to two kings and one regent were well rewarded with numerous grants of lands and wardships in England and Ireland. His relatively rapid rise through administrative service and his position of influence over the king as a prominent member of the household led to resentment among some English magnates, and his participation in the exclusion of Archbishop Stratford from the parliament at Westminster in 1341 did little to enhance his reputation. He was the longest serving justiciar of Ireland in the fourteenth century. His three active terms in office may be considered successful, particularly given the troubled events that provided the backdrop to the first two. Though not directly involved in the government of Ireland in the 1340s, he actively advanced the career of Roger Darcy, the second son of his first marriage, who successively became escheator, deputy chancellor, and deputy justiciar of Ireland.