Walter was born at Islip, Oxfordshire. He was a cousin of Simon Islip, Archbishop of Canterbury, and no doubt his career benefited as a result, though he was some years older than Simon. His patron in his early years was Richard de Ferings, Archbishop of Dublin; he probably arrived in Ireland in the Archbishop's entourage in 1299. - Walter was an Islip native Throughout his career Walter moved back and forth between Ireland and England. In Ireland he initially lived at the Priory of Kilmainham, but later purchased the manor of Thorncastle, in south Dublin County, which is roughly present day Mount Merrion. He also had a town house in Dublin; there is a reference to Dublin Corporation supplying his house with water. He developed strong links with Kilkenny, where he usually lodged with the Outlaw family, who were at the heart of the Witch trials.
Career
In 1308 he was chosen as one of the Barons of the new Court of Exchequer ; he was given the title of Chief Baron in 1309, but stepped down from office in 1311. He is mentioned again as a Baron of the Exchequer in 1335. He was appointed Chief Escheator of Ireland in 1310. He served three terms as Lord Treasurer between 1314 and 1325. In 1325 he attended a seemingly routine Exchequer audit in London, where grave irregularities came to light. Serious questions were raised about Islip's integrity, and in one of the first examples of an official inquiry in Ireland, a Dublin jury was selected to determine the truth of the allegations of fraud and corruption against him. Alexander de Bicknor, the Lord Chancellor of Ireland, was accused of the same offences. Islip was finally removed from office as Treasurer, and imprisoned for a time in the Fleet Prison. In 1334 he was ordered to repay the Crown the considerable sum of £1332, and in default of repayment most of his Irish lands were forfeited. In 1336 he obtained a royal pardon for all his faults and transgressions. He also held office as Custos rotulorum for Kilkenny. In 1329 he was engaged in litigation with one William de London; the striking feature of the case was that de London was represented by one of Islip's colleagues on the Bench, John de Grauntsete. Such conduct seems to have been unheard of even at the time: Cohen calls it "startling" and probably without parallel in legal history. De Grauntsete was soon afterwards removed from the Bench for a time: the reason for this was apparently not his conduct in Court, but the fact that he had read out letters of excommunication from the Pope.
The Kilkenny Witch Trials of 1324, in which the principal accused were Alice Kyteler, her son William Outlaw and Petronilla de Meath, deeply divided the Anglo-Irishruling class. This was partly because many of them were connected to Alice through her four marriages, and partly because the Bishop of Ossory, Richard de Ledrede, the driving force behind the prosecutions, was bitterly unpopular. Islip seems to have been firmly on the side of the accused : as Custos of Kilkenny he refused to order their arrest, and was probably a party to the Bishop's own arrest and brief imprisonment.
