 Valentine established connections with several powerful figures at court, including by 1613 Robert Carr, 1st Earl of Somerset, a favourite of James I. Somerset's fall from favour in 1615 reduced Valentine's influence, and he was briefly imprisoned for debt in 1619.Valentine then attached himself to the retinue of William Herbert, 3rd Earl of Pembroke and sought to undermine the royal favourite George Villiers, 1st Duke of Buckingham, with limited success.He became intimate with Sir John Eliot through his opposition to Buckingham, and Eliot arranged for him to be elected on 3 March 1628 to represent the borough of St. Germans in the Parliament of 1628–9.