Knollys came from a cadet branch of a family established in Hertfordshire by the 14th century, which first leased Rotherfield Greys in 1514 and later acquired the freehold. His great-grandfather, Sir Francis Knollys, sat in the Reformation Parliament and represented Oxfordshire seven times under his kinswoman Elizabeth. The estate, worth about £800 p.a. but seriously encumbered, was settled on trustees for Knollys’s benefit at his marriage. By absenting himself for five weeks from his house during the Civil War to escape ‘the violence and disorders of the soldiers’, he became a technical delinquent, though he had contributed £550 to the county committee, and even before his offence the parliamentary forces at Henley had felled timber to the value of £2,000, besides defacing the house for military purposes. He compounded for £1,100 in 1648. He apparently remained quiet during the Interregnum, but early in 1660 was among the Oxfordshire gentry who signed the address for a free Parliament.3Lee, 595; Her. and Gen. viii. 297, 299; Cal. Comm. Comp. 996; SP 23/175/653-4, 657; Bodl. Wood, 276A/221.
Knollys was a partner in the local excise farm in 1662, and was returned for the county after a contested by-election in the following year. During his brief service in the Cavalier Parliament he was an active Member. He was appointed to 14 committees, of which the most important were to prevent unlawful meetings of dissenters and to consider the additional bill to regulate the excise. He was buried on 4 Sept. 1664 at Rotherfield Greys. His son, the last of this branch of the Knollys family, died six years later.4CJ, viii. 506; Cal. Treas. Bks. vii. 1109, 1253-4; PCC 60 Mico.