Thomas Allen (or Alleyn) (21 December 154230 September 1632) was an English mathematician and astrologer. Highly reputed in his lifetime, he published little, but was an active private teacher of mathematics. He was also well connected in the English intellectual networks of the period. Early life He was born in Uttoxeter, Staffordshire. He was admitted scholar of Trinity College, Oxford, in 1561; and graduated as M.A. in 1567. In 1571 he left his college and fellowship, and moved to Gloucester Hall. He became known for his knowledge of antiquity, philosophy, and mathematics. At Gloucester Hall Gloucester Hall suited Allen, a sympathiser at least with Catholicism, because there was no stringent religious observance required there; indeed there was no chapel in the Hall. Allen's beliefs have been classified as "church papist", but also his posture as "crypto-Catholic": a Catholic faith combined with outward conformity to the Church of England. He joined there his friends Edmund Reynolds, Miles Windsor, and George Napper, who had also left their colleges at a time of increasing religious tensions on Oxford; Napper was to be a Catholic martyr. Trinity shed six more of its Fellows within a few years. Allen encouraged other scholars to migrate there, such as John Budden and William Burton. He had a wide range of pupils and followers: Kenelm Digby and Brian Twyne in natural philosophy, with Theodore Haak coming later. The mathematical school of Allen included Thomas Harriot and Walter Warner, and Sir John Davies (to whom Allen taught Catholic doctrine). Mathematical geography was an important topical subject in which Allen was reputed, pursued by several groups in England, including another around Henry Briggs: Allen may have taught the geographer Richard Hakluyt. He did teach Robert Fludd and Sir Thomas Aylesbury. In the humanities there were Robert Hegge, and William Fulbecke. When the Camden Chair of Ancient History was being set up in the early 1620s, Allen successfully supported the candidacy of Degory Wheare with William Camden; and a few years later, in 1626, Wheare came to Gloucester Hall as Principal. Allen died at Gloucester Hall. Other associations Allen corresponded with Henry Percy, 9th Earl of Northumberland. Northumberland invited Allen to visit, and he spent some time with the Syon House group around the Earl; he became acquainted with Thomas Harriot, John Dee, and other mathematicians. He also knew well Sir Robert Cotton, William Camden, and their antiquarian associates. He pointed