father was Henry Percy, 4th Earl of Northumberland. Thomas was the great-grandson of Henry Percy, 4th Earl of Northumberland, and the second cousin once removed of the 4th Earl's descendant, Henry Percy, 9th Earl of Northumberland. He was born around 1560 and matriculated at the University of Cambridge as a member of Peterhouse in 1579. Little is known of his early life. He may have been a papist before he was at some point received into the Catholic Church, and he may have sailed with George Clifford, 3rd Earl of Cumberland, in 1589. In 1591 he married Martha Wright, daughter of Ursula Wright (a convicted recusant) and sister to Christopher and John Wright (both later involved in the Gunpowder Plot). Claims by several authors that Percy may have left Martha "mean and poor" for an unidentified woman in Warwickshire are disputed, but the two were at least estranged: in 1605 Martha and her daughter were living on an annuity funded by the Catholic William Parker, 4th Baron Monteagle. Thomas and Martha's son, Robert, married Emma Mead at Wiveliscombe in Somerset on 22 October 1615. Despite not being a close relative, in 1595 the 9th Earl of Northumberland made Thomas responsible for collecting rents from his northern estates, and the following year appointed him constable of Alnwick Castle. Thomas exercised his authority in a manner which gave some cause for complaint, not least from an officer he replaced, and contemporary reports of his dealings with the earl's tenants include claims of mismanagement and bribery. During a border skirmish he killed James Burne, a Scot, for which he was imprisoned at a London gaol, but his release was secured by the intervention of Robert Devereux, 2nd Earl of Essex. Thomas subsequently aided Essex in a conspiracy against the Scottish warden of the middle marches, although unlike several others who later joined the Gunpowder Plot, he was not a member of the earl's failed rebellion of 1601. Percy was a tall, physically impressive man, "of serious expression but with an attractive manner". He has been variously described as belligerent and eccentric, with "surges of wild energy subsiding into sloth". The Jesuit priest Father John Gerard wrote that in his youth Percy had "been very wild more than ordinary, and much given to fighting", while the Jesuit Oswald Tesimond thought he had been "rather wild and given to the gay life, a man who