The Lowthers were an old and distinguished family, with an impressive record of parliamentary service dating back to the very beginning of the 14th century. Their principal seat lay at Lowther castle near Penrith, although over the years they acquired other property, including the manors of Allerby, Crosby, Newton Reigny and Wythorp in Cumberland. Each of the five knights who headed the family before Robert succeeded to his inheritance represented one or other of the two counties of Cumberland and Westmorland in the House of Commons, as well as playing an active part in local government, so Robert was heir to a long tradition of involvement in the affairs of the north-west. His father, Sir John, who is reputed to have been one of Thomas, Lord Clifford’s tutors, died at about the same time as his grandfather; and it seems likely that Robert had just taken possession of their estates when, in December 1382, he was appointed to the Westmorland bench. It was his uncle, Robert Lowther the elder, who became keeper of Carlisle castle three years later, and since he himself was removed from the commission of the peace in 1386 this part of his life remains fairly obscure. He did, however, serve as a tax collector and royal commissioner before entering the House of Commons in 1391 for the first time. His younger brother, William I, was returned to the next Parliament, in 1393, then he himself sat again one year later. During this period he established a connexion with the Nevilles which was to last for the rest of his life, being made deputy to Ralph, Lord Neville (cr. earl of Westmorland 1397) as keeper of the royal forests north of the Trent. His marriage to Sir John Derwentwater’s widow, Margaret, also improved his standing in the community, for besides bringing him the manors of Castlerigg and Tallentire in Cumberland, which she held as dower, Margaret was also heiress, through her mother, to land in the Westmorland villages of Ormesby, Soulby and Warcop. After her mother’s early death, in about 1365, Margaret’s father, William Strickland, had taken holy orders, and for some time he served as chaplain to Thomas Appleby, bishop of Carlisle. So successful was he, that in 1396 the chapter chose him to succeed Appleby, although he had to wait another four years before changing political circumstances made possible his consecration as bishop. Naturally enough, Strickland’s influential position—no less than the fact that he enjoyed the support of the new Lancastrian regime—worked to the advantage of his son-in-law, who benefited considerably from his advancement. Robert and Margaret were married well before September 1398, when they secured a papal indult to make use of a portable altar, having almost certainly by then produced at least two of their six sons and three daughters.
Although he agreed to act as an attorney for both John Fyne and his own distant kinsman, Sir Peter Tilliol, when they took part in Richard II’s ill-fated expedition to Ireland in the spring of 1399, Robert’s sympathies clearly lay with Henry of Bolingbroke and his supporters. Nor did his official position as King Richard’s lieutenant in Inglewood forest prevent him from throwing in his lot with the new government. His election to the Parliament of 1401 must have owed something to the influence of his brother, William, who, as sheriff of Cumberland, made the return on this occasion. The two men were certainly very close, since they attended the Parliament of January 1404 together, clearly with the intention of pursuing their own private interests. The House of Commons was still sitting when they negotiated two separate leases of property in Inglewood forest, each naming the other as a mainpernor at the Exchequer. In May 1406, Sir Robert again seized the opportunity offered by his Membership of the Commons at Westminster to enter another contract for the farm of three closes and a fishery in the forest, this time for a longer term of 20 years. By then, he and his brother were beginning to carve out for themselves something of a monopoly in the area of local government. They were named together, in February 1405, as collectors of the lucrative wool custom at Carlisle; and five months later both were commissioned by Henry IV to take possession of Cockermouth castle, which had been forfeited by the rebel earl of Northumberland. In the following year Sir Robert succeeded William for his second term as escheator of Cumberland and Westmorland. William was immediately made sheriff of Cumberland, being duly replaced by Sir Robert, in 1407, when he left office.
Meanwhile, Sir Robert attended the elections held at Carlisle to the Parliaments of 1413 (May), 1414 (Nov.), 1416 (Mar.), 1421 (May and Dec.), 1422, 1423, 1425 and 1426, as well as being returned again himself to the Parliaments of 1414 (Apr.) and 1417. On the latter occasion, he and his colleague, Sir Peter Tilliol, joined with Robert Warcop in taking a bond worth £100 from Robert Warcop in taking a bond worth £100 from John Lancaster I.
Sir Robert was buried, according to his wishes, in the choir of the parish church of Lowther. He left 100 marks for the celebration of masses for his own soul and that of his late father-in-law, the bishop. He was evidently involved in sheep farming on an impressive scale, since his widow and younger offspring shared four large flocks between them. The task of executing his will fell to his widow, Margaret, his second son, William II, and his friend, Thomas More II. His eldest son, Hugh, whom he had helped to return to Parliament as a shire knight for Cumberland for the first time in 1426, succeeded to his estates immediately. Dower was assigned to Margaret, who lived on at Lowther for another 19 years. She died in July 1449, having asked to be buried next to her father in the cathedral at Carlisle, where masses were to be said for him and for both of her late husbands.