Although it is possible that they were one and the same person, circumstantial and chronological evidence suggests that the subject of this biography was either the son or kinsman of the Ralph Mackerell who served as a tax collector in Derbyshire over the decade ending in 1393. Not much information has survived about his early life, but he apparently inherited property in and around Breaston, in the same county, which had been in the hands of the Mackerell family for some years. When he died, Mackerell was also seised in his own right of the neighbouring manor of Wilsthorpe as well as land in the environs of Sandiacre; and this, together with his extensive holdings at Carlton in Lindrick, Blyth, Clipston, Fenton, Stretton, Hayton Muskham and elsewhere in Nottinghamshire, may likewise have come to him, in part at least, by inheritance.
Meanwhile, in the early spring of 1408, Mackerell appeared as defendant at an assize of novel disseisin arraigned against him at Nottingham by (Sir) Nicholas Strelley and others, probably as a collusive suit designed to secure their title to property. His involvement in the business of local government began in earnest two years later; and in 1414. not long before the start of his first term as sheriff, he attended the Nottinghamshire parliamentary elections. A mark of his standing at this time may be found in the award to him and his wife of a papal indult permitting the use of a portable altar; and it is thus hardly surprising that the local gentry chose to return him as their representative to the second Parliament of 1414. In the following year Mackerell and his wife leased out part of their estates at Hodsock to a neighbouring farmer, and subsequently made a release of all legal actions to the Staffordshire landowner, Sir Robert Francis, whose daughter had by then married Mackerell’s stepson, Gervase Clifton. By the time of his second appearance in the House of Commons, in December 1420, Mackerell had gone surety at the Exchequer for one of his neighbours, and had also discharged a period of garrison duty at Berwick-upon-Tweed, under the command of Richard, Lord Grey of Codnor. His experiences on the Scottish border more than qualified him for his next appointment, as deputy keeper of Nottingham castle. He had probably been in office for quite a while, when, in February 1421, an assignment of £40 was made to him by the government for necessary repairs. A number of important prisoners captured by Henry V in France were housed in the castle, and Mackerell spent some time during this period escorting them to and from London for examination before the royal council, incurring expenses of over £64 for their transport and lodging.
In his capacity as sheriff of Nottinghamshire, Mackerell was responsible for holding the elections to the Parliament of 1422, during which his close friend, John Allestre, was chosen as one of the Members for the borough of Nottingham. Allestre had just named him as the supervisor of his will (the monetary provisions of which came to almost £500), although he can hardly have required much outside help to obtain a seat at Westminster. Mackerell attested the writ of return for Nottinghamshire to the Leicester Parliament of 1426, putting himself forward as a candidate in the following year. The circumstances of his election, on 25 Aug. 1427, raise some interesting questions, for although he was clearly a popular and influential figure in the county community, which he had, indeed, represented twice before, his conduct on this occasion was manifestly unconstitutional. Not only did the sheriff, Sir Thomas Gresley, choose him and his colleague, Hugh Willoughby, without having first received the necessary writ of summons, but he also refused to hold any form of election and compounded his offence by making the return under his own seal, rather than in the form of the indenture required by law. In accordance with the statute of 1410 (which clearly laid down the procedure to be followed in cases of electoral malpractice), an inquest was taken at Nottingham on 27 Feb. 1428 before specially commissioned justices of assize, but since Parliament was then well into its second session, the verdict of the court had little practical effect other than to deprive Mackerell and Willoughby of their expenses and cause Gresley to forfeit the statutory fine of £100. The presentation of a parliamentary petition at this time designed to safeguard the legal position of both sheriffs and shire knights whose conduct gave rise to such inquiries (and also attempting, unsuccessfully, to have the findings of any such investigations set aside) was clearly prompted by this case, and must have owed a good deal to the efforts of the two Members for Nottinghamshire and their friends.
When he died, in January 1436, Mackerell was able to leave his widow securely in possession of almost all his own extensive holdings. He thus prevented the Crown from asserting its claim to wardship during the minority of his eldest son, Hugh, who was then 16 years old, and presumably the child of his second marriage. The boy had at least two younger brothers, both of whom were named as beneficiaries of the will of their grandmother, Alice (d.1439), the widow of the Nottingham merchant, John Tansley. The estates which Mackerell had retained in the right of his first wife, Katherine, reverted to his middle-aged stepson, Sir Gervase Clifton.