1601 he was for a short time in private custody (Cal. State Papers, Dom. 24 Feb. 1601). After the execution of his father the young Lord Essex was entrusted to Savile's charge at Eton, and subsequently seems to have been treated with great deference at Merton, being specially allowed one of the rooms in the warden's lodging.
Savile's relations with Essex, and his ability as a scholar, secured him the favour of King James, by whom he was knighted after a banquet given to the king at Eton on 30 Sept. 1604 (Winwood, Memorials, ii. 33). He is said to have declined offers of further preferment by James in either church or state (English Baronetage, i. 60). Though in favour at court, he was sufficiently independent to run the risk of giving offence by his refusal to sanction at Merton the sermon ordered to be preached every Tuesday by members of each college in commemoration of the king's escape from the plot against his life (known as the Gowrie plot) in Scotland (Mem. Merton Coll. p. 70). He was appointed to correct the Latin translation of the king's ‘Apology for the Oath of Allegiance’ (Cal. State Papers 27 April 1609), and was among the scholars commissioned to prepare the authorised translation of the bible; portions of the Evangelists, the Acts of the Apostles, and the Book of Revelation fell to his share.
The loss of his only son in 1604 was probably one of the causes which induced Savile from that time onward to devote the greater part of his fortune to the advancement of learning. He had long contemplated an edition of St. Chrysostom, and had visited for the purpose all the public and private libraries in Great Britain (Preface to the St. Chrysostom, vol. viii.). Through agents in the various capitals of Europe and the intervention, on their behalf, of the English ambassadors, Savile now collated all known editions and obtained examinations of the best manuscripts. He also received assistance from Greek scholars abroad (Preface, vol. viii.), and gathered round him at Eton men of learning like Richard Montagu, Hall, Boys, Carleton, and Allen. After making an attempt, but failing, to secure the Royal French type for the work (M. Pattison, Life of Casaubon, p. 231), he purchased a special fount from Holland, engaged John Norton, the king's printer, for the task, and himself supervised the whole of the printing at Eton [see under Norton, William]. The first volume of the great work was published in 1610; it was completed in eight volumes folio in 1613. Its preparation is said to have cost Savile 8,000l., the paper alone costing 2,000l. The sumptuous undertaking was the first work of learning on a great scale published in England (Hallam, Hist. of Lit. of Europe, iii. 10). Casaubon (in ‘Epist. ad D. Hoeschelium’) speaks of it as prepared ‘privatâ impensâ animo regio.’ There seems to have been considerable difficulty in disposing of the thousand copies. The price was at first fixed at 9l., subsequently at 8l. (Savile to Carleton, 26 Feb. 1613, Cal. State Papers, Dom.), but after Savile's death a few copies in the possession of Eton College were sold for 3l. Through Dudley Carleton, who was the son-in-law of Savile's wife, presentation copies were given to the Signory of Venice and to the states of Holland, and through the same agency copies were sold abroad. Savile, however, writing to Carleton, 13 March 1615, laments that the ‘market for the Chrysostom is so down’ (Cal. State Papers, Dom.). The sale of the work is said to have been greatly interfered with by the publication in Paris, two years later, of a similar edition by Fronton Du Duc, with a Latin translation attached; the Latin text, according to Fuller, was derived from proof-sheets of Savile's work, which had been secured by fraud. But though Savile's text appears to have been employed, there is no evidence that it was fraudulently obtained (Brunet, Manuel du Libraire, iii. 535). In 1613 Savile continued the work of his printing press at Eton by editing Xenophon's ‘Cyropædia,’ and in 1618 he published for the first time, at the request of Abbot, archbishop of Canterbury, Thomas Bradwardine's ‘De Causa Dei contra Pelagium.’
Savile had always been a close friend of Bodley (Bodley's will quoted in Macray's Annals of the Bodleian, p. 407), and assisted the latter in the foundation of his library (Wood, Hist. of Oxford, iii. 928). Possibly stimulated by Bodley's munificence, he founded the two professorships which still bear his name in the university of Oxford. In the preamble of the deed of foundation (dated 1619) it is said that geometry is almost totally unknown and abandoned in England, and it was to remedy this evil that Savile established the two Savilian chairs of geometry and astronomy open to mathematicians from any part of Christendom. The professorships were each endowed with 150l. per annum, a mathematical library established for their use, and a mathematical chest furnished with 100l. Savile himself gave in act week 1620 (ib. ii. 334) the first lectures in geometry, which were published in 1621, together with some of his earlier mathematical lectures. When Camden was on the point of founding his professorship at Oxford, Savile