Shilleto’s family had been resident in the Pontefract area since the fourteenth century. His grandfather, a Crown tenant of the demesnes and coalmines of Great Houghton, styled himself a yeoman in his will, though he was granted arms in 1604.
Shilleto’s appointment in 1606 as one of the four attorneys in Star Chamber represented a significant promotion, which is difficult to explain; it was presumably linked to his marriage with one of the premier families of North Wales, or perhaps to the man who thereby became his brother-in-law, Sir Edwin Sandys*.
At the hotly contested Yorkshire election of December 1620 Shilleto, then high constable of Agbrigg wapentake, canvassed the freeholders for Sir Thomas Wentworth*. The latter’s opponent, Sir John Savile*, complained to the Commons about a multitude of sharp practices, but the only charge taken seriously was that Wentworth had used the West Riding constables to canvass for him. On 13 Feb. Shilleto testified that he had been asked to establish the level of support for Wentworth in his bailiwick, but had not been compelled to return the names of refusers. This suggested that two other constables who had ordered the freeholders to turn out for Wentworth had exceeded their instructions, and this allowed the House to confirm the election result on 23 March.
Shilleto left no trace on the Commons’ debates before the summer adjournment, but made two recorded speeches in the autumn. On 27 Nov., amid official calls for speedy supply for relief of the beleaguered garrisons of the Palatinate, he suggested that an expedition be sent to intercept the Spanish plate fleet in the Caribbean instead. However, this serious point was lost when he attempted to justify this belligerent policy with a precedent from his own court of Star Chamber.
Wentworth required one of the Pontefract seats for himself in 1624; Shilleto does not appear to have stood at the general election, and when the other seat was vacated early in the session, it was contested by Sir John Jackson* and Sir Richard Beaumont*. The latter was initially reluctant to face another contest in 1625, recommending Sir Henry Savile* or Shilleto as his replacement, but ultimately changed his mind. Shilleto remained a Wentworth supporter, joining the latter in refusing the Forced Loan in 1627, while as late as 1635 lord keeper (Sir Thomas) Coventry* mentioned to Wentworth Shilleto’s ‘zeal in your service’. That same year Shilleto allegedly intervened in a controversial Star Chamber suit involving his Bulkeley relatives.
The final years of Shilleto’s life were overshadowed by difficulties over his accounts as duchy receiver, as a result of which he was imprisoned in the Fleet. He died intestate, and administration of his estates was granted to his widow on 15 Nov. 1637. No other member of the family entered Parliament.