Sir Robert’s ancestors are known to have lived at Plumpton from at least the 1160s onwards, and by the time of his birth the family had come to enjoy considerable influence in the north, not least because of his grandfather’s marriage to Isabel, the daughter of Henry, 1st Lord Scrope of Masham. The Plumptons were determined to consolidate their position even further by finding a wealthy bride for Robert, and with this purpose in mind in 1392 his father, Sir William, purchased the marriage of the infant Alice Foljambe from her uncle and guardian, Sir John Leek. Alice was the great-grand daughter and heir of Sir Godfrey Foljambe, sometime steward of the duchy of Lancaster and owner of widespread estates in Nottinghamshire, Derbyshire and Warwickshire. Although part of these holdings remained in the hands of dowagers (not least Alice’s mother, who married Sir Thomas Rempston I, one of Henry IV’s leading adherents, and lived on until 1454), the rest of the Foljambe inheritance, which included the manors of Kimbolton and Mansfield Woodhouse (worth at least £20 a year) in Nottinghamshire, and the manor of Whittington in Warwickshire, together with property valued at £40 p.a. in Derbyshire, greatly augmented the wealth and authority of the Plumptons, whose territorial influence had hitherto been confined to Yorkshire. Custody of these estates was duly accorded to Robert and his wife once the latter reached the age of 14 in November 1401, and for the next four years they lived peacefully at Kinoulton.
Sir William Plumpton’s decision to throw in his lot with his uncle, Richard Scrope, archbishop of York, and rise against Henry IV in open rebellion, disrupted this period of calm, and led, in June 1405, to his execution along with that of the archbishop, outside the walls of York. Sir William’s head was displayed on the Micklegate as a warning against further acts of treason, and eventually dispatched to his widow two months later, possibly on the orders of her brother-in-law, William Frost, who was then governing the city. In other respects, however, the King showed great clemency towards the family, allowing the widowed lady Alice to retain the Plumpton manors of Grassington and Studley Roger (which had been temporarily forfeited after the uprising) and also permitting her to keep goods to the value of £40 out of her late husband’s estate so she could support the ten children still in her care. In point of fact, her complaints of poverty and destitution cannot be taken too seriously, for she was (with her sister, Isabel Frost) coheiress of the wealthy merchant, John Gisburn, a former mayor of York, who left extensive property there and in Ripon. Although Robert, as successor to both his father and grandfather, did not stand to inherit any of these holdings, which were entailed to provide for his many siblings, he none the less agreed to house and feed his new dependants, and in October 1405 he and his mother entered into an agreement whereby she and her younger children were assured of board and lodging at Kinoulton. The generous bequests made to them all by their maternal grandmother, Ellen Gisburn (who left Robert and his brothers £10 each) at this time clearly eased the financial strain. Moreover, King Henry was too shrewd a politician to allow Sir William’s treason to poison his relations with the rest of the Plumptons for long; and he soon issued royal pardons to Robert and his grandfather. The latter was even confirmed in the annuity of £20 which had previously been awarded to him by John of Gaunt from the revenues of the lordship of Pontefract, so that by his death, in April 1407, the process of rehabilitation was virtually complete.
Since his mother had retained all the late Sir William’s estates as a jointure, it was not until his grandfather died that Robert Plumpton actually gained possession of any family property in Yorkshire. The survival of his widowed grandmother, Isabel, who enjoyed a life interest in the manor of Plumpton, further reduced his inheritance, but he was at least henceforward able to count upon additional revenues in the order of £20 a year from the manors of Idle, Nesfield and Steeton.
Already aware of the need to make provision for his younger children in the event of his own death, Sir Robert now placed his Yorkshire estates in the hands of trustees, among whom was Henry, Lord Fitzhugh, the King’s chamberlain and treasurer of the Exchequer, under whose command he left Southampton, in April 1418, to take part in Henry V’s reduction of Normandy. Just before his departure he arranged for annuities of 20 marks each to be settled upon his two younger sons; and he also set aside sums for the marriage of his daughters. He was, indeed, still in France, when, in June 1419, a contract was drawn up for the betrothal of Joan (the elder) to one William Slingsby of Scriven in Yorkshire, who undertook to set aside lands worth 40 marks a year for her use. Within a few weeks, however, Sir Robert returned to supervise his affairs in person, arranging for the upkeep of a family chantry at Esholt in Yorkshire and also devising another settlement of his estates which at last included his grandfather’s seat at Plumpton. His friend and kinsman, Sir Thomas Rempston II, who had also been involved in the negotiations for Joan’s marriage, figured prominently on this new, and, in the event, final list of feoffees.
Sir Robert returned to the theatre of war in October 1420, when he left Portsmouth with a private retinue of eight archers who were to fight under his command in the royal army for the next year. He is said to have fallen at the siege of Meaux, and his death, on 8 Dec. 1421, certainly coincided with the bombardment of the town. He was succeeded by Sir William Plumpton, his eldest son, a redoubtable figure, who, like his father before him, served as steward and constable of Knaresborough. His wife, Alice Foljambe, had predeceased him by at least two years, but his mother lived on until the winter of 1423.