Thomas was the eldest son of Richard Blagrave of Uttoxeter in Staffordshire. He seems to have moved down to Berkshire along with his uncle, Robert. While Robert settled in Reading and became the ancestor of the famous Blagraves of that town – including his grandson, the famous mathematician – Thomas may have tried his luck in Newbury. He managed to secure himself a position in the employ of Thomas Cawarden, a Groom of the Privy Chamber, to whom the King had given the stewardship of Donnington Castle, Benham Park and other West Berkshire manors. He was probably present when King Henry visited Donnington in 1541. Three years later, Cawarden was appointed Master of the Revels with responsibility for overseeing and financing all Royal entertainments from his offices in Blackfriars. Blagrave presumably then spent much time in London and was working in the Revels Office itself by 1446.

By 1551, Thomas was appointed Deputy Clerk of the Revels, one of the officials undertaking the book-keeping at the Revels Office, and it was probably during this period that he made an advantageous marriage to Joan, the daughter and heiress of William Bellamy of Hadley in Middlesex. They had at least one son and four daughters together, one of the latter of whom eventually married William, the brother of Thomas Lodge, the poet and playwright. Having presumably kept his head down during the religious turmoil of the period, Blagrace was appointed Clerk of the Revels under Sir Thomas Benger in 1560. He was paid eight shillings a day, with an additional twenty-four shillings a year for livery. He was also given a large hall house with seven bedrooms and stabling to live in at the former hospital of St. John of Jerusalem in Smithfield to where the Revels Office had by then moved. It appears to have been around this time that Blagrave became associated with the Protector Somerset’s son, the 2nd Earl of Hertford. Thomas leased much land from him in his home parish of Great Bedwyn in Wiltshire, including a new home at Grafton Court. This was shortly before his lordship was locked up in the Tower of London for marrying the Queen’s cousin without her permission. Blagrave became the Earl’s auditor during his years of imprisonment and even sat as MP for Great Bedwyn in 1571. Benger was an ineffectual Master and stepped down in favour of Blagrave in 1573, although he was never officially appointed and remained Acting Master of the Revels to Queen Elizabeth I throughout his term of office. This did have the advantage of enabling him to draw a salary from both positions. Throughout his time in office, Blagrave had to organise all manner of entertainers and workmen involved in acting, acrobatics, building sets and making costumes. The most frenzied activity took place around Christmas and Shrove Tuesday and he would watch all the rehearsals at St. Johns. After the 2nd Earl of Hertford’s release from the Tower of London, he seems to have fallen out with Blagrave, who he accused of misappropriating the tithes from Bedwyn Parsonage and embezzling £800 along his receiver, William Drury.

After Benger’s death in 1577, Blagrave hoped for a formal appointment as Master of the Revels, but he was not high enough up the social structure and it was given, over his head, to Edmund Tilney, an associate of Lord Howard of Effingham. Blagrave remained the Revels Clerk, but thenceforth avoided his duties there. In recompense for his loss, he was made Surveyor of the Queen’s Works, a position roughly equivalent to being Royal Chief-Architect. He had presumably gained much experience in building theatrical stages and other temporary structures in his role as Master of the Revels. He may even have been involved in the building of the ‘Theatre’ playhouse which he had licensed in 1576. Soon afterwards, Blagrave’s son, John, had certainly designed new improvements in brick kiln and furnace construction. It has also been suggested that Thomas undertook a major building project as the architect of Shaw House, built between 1578 and 1581 near his Wiltshire and Berkshire homes.

Blagrave continued in office until his death on 18th June 1590, when he was buried in St. James’ Church in Clerkenwell. He was succeeded by his son, John, who continued at Grafton Court in Bedwyn. A later Assistant Master of the Revels, under Sir Henry Herbert in the 1630s, named William Blagrave may have been his grandson, although he does not appear in the traditional pedigrees.