Upton is first recorded in June 1409 when, on the instructions of Robert Hugford, overseer of the estates of Richard, earl of Warwick, he rode to London on the earl’s business. His name appeared on the list of the earl’s retinue destined for Calais in 1415, and two years later he began to serve under him as bailiff of Warwick. By 1424 he is known to have owned a house in the town, situated in the horsefair opposite the church tower, and he also possessed a tenement in Castle Street and another property (later called Berkeswell Place), which last he sold to St. Mary’s college in 1443.
Upton regularly attended elections held at Warwick; he witnessed the indentures recording the borough elections to the Parliaments of 1419, 1420, 1422, 1423, 1425, 1426 and 1435, those recording the returns for both the borough and the shire in 1429, 1432 and 1433, and those for the shire alone in 1425 and 1437. He is known to have discharged office as bailiff of Warwick (presumably by appointment of the earls of Warwick who were lords of the borough) for at least eight terms, and his name frequently appears as a witness to local deeds.