The Middle‑aged sources prove the presence of the English knights in Prussia who were guests of the Order of the Teutonic Knights and as crusaders took part in campaigns against Lithuanians. Wigand of Marburg, a chronicler, mentions by name only one of such guests, that is, Thomas de Offart. In the literature the very knight is commonly identified with Thomas Ufford, Robert’s son, the first earl of Suffolk and lord Ufford. Here, however, Thomas is called an earl by Wigand. This is a mistake as the title of a count/earl belonged only to Robert and his son William. What is most intriguing, however, is Thomas’s age seen by Wigand in Prussia in 1331. The key‑role here is played by the wedding date of Robert and Margaret of de Norwich. The very couple, according to all sources available, got married in 1324 or, more generally, in the 1320s. In this situation, Thomas certainly could not reach the legal age in 1331. What proves it is a note in Chronica minor Sancti Benedicti de Hulmo where the Thomas’s birthday was given, namely the day of Mary Magdalene in 1332. However, there exist speculations according to which this Thomas, although was not Robert Ufford’s son, could be his younger brother. Basing on the sources and research by W. Betham and R.E.Ch. Waters, Thomas’s birthday, earl Robert’s brother, can be dated between 1300 and 1306. That is why Thomas, when being in Prussia, could be 26. Mistaking earl’s brother for his son called the same could be connected with a big popularity ascribed to the names of both Robert and Thomas in the family of Uffords. Earl Robert’s father was also Robert, but only lord Ufford, not an earl. Both had a son and a brother called Thomas. The very mistake was probably already made in the Middle Age or later when Konrad Gesselen translated the chronicle asked to do so by Jan Długosz.