Nothing is known about Sirla’s background, or whether his family originally came from Dorset. His first appearance in the records is on the return to the Parliament of 1431, as one of burgesses for Weymouth, the borough he was to represent twice more in the same decade. That he was well regarded locally is also indicated by his election as bailiff of the town at Michaelmas 1434, and the fact that at the end of his term he was chosen as an MP for the third time. It may be that as out-going bailiff he was required to present some accounts at the Exchequer. While up at Westminster in that Michaelmas term of 1435 he appeared in person in the court of common pleas to bring two suits. First, he alleged that William Whitling, parson of the church at nearby Portland, owed him £40, and then he assisted a woman from Weymouth, Edith Penne, widow and administrator of the goods of Robert Penne†, to forward her plea against those responsible for the estate of the late William Wyot*, the local merchant who had died owing Penne £26.
Sirla’s fellow Member for Weymouth on the last occasion he sat had been John Bassingbourne, who did not survive for long after the Parliament ended. Sirla married his widow, Alice, and as a consequence he became a party to lawsuits in which she was engaged as her late husband’s executrix. Thus, in Hilary term 1438 he and Alice were sued by the widow of John Crouk† of Bridport for a debt of £19.
Sirla was considered to be of sufficient standing in Dorset to be appointed a tax collector in the county in 1445. Much less to his credit, in Michaelmas term that year he was named among the 50 followers of Sir James Butler, afterwards earl of Wiltshire and Ormond, accused in the King’s bench of participating in the murder of Robert Fayrechild at Toller Porcorum in August 1444. Fayrechild had died in the first of the violent clashes prompted by the quarrel between Butler and his wife’s uncle William Stafford*. Sirla, alleged to have been an accomplice rather than a principal in the affair, was described in the court proceedings as resident at Hooke, Butler’s seat in Dorset. The principals successfully sued for royal pardons on 11 May 1446, and Sirla did likewise on 14 July. The pardon gave him the alias of Nygge or Ning, and his addresses as Weymouth and Wyke Regis.
Both the surnames used by the MP were very uncommon, which raises the possibility that William Nyng, who married one of the daughters and coheirs of Thomas Winslow II*, the London draper, was a kinsman of his. Winslow sat for another Dorset borough in 1455.
