He was educated privately under a tutor, was for a short time at Great Grimsby grammar school, and afterwards matriculated at St Catharine's College, Cambridge in 1627[1] or 1629.

In 1644 he preached in London and Suffolk churches and churchyards, and occasionally, in what afterwards became quaker fashion, endeavouring to supplement the regular sermon by a discourse of his own.

[3] In 1645, with Benjamin Cox and others, Knollys was the author of A Declaration concerning the Publicke Dispute which should have been in the Meeting House of Aldermanbury, December 3 1645, concerning Infant Baptism.

A letter (11 January 1646) from him to John Dutton of Norwich, in favour of toleration, printed by Edwards in Gangraena, embittered the presbyterians against him.

On the outbreak (7 January 1661) of Thomas Venner's insurrection he was committed to Newgate Prison on suspicion, and detained till the act of grace on the king's coronation (23 April) liberated him.

[3] In London he once more resumed his school and his pastorate, preaching also a morning lecture on Sundays at Pinners' Hall, Old Broad Street, then in the hands of independents.

He was committed to the Bishopgate compter, but was considerately treated and was allowed to preach to the prisoners; at the next Old Bailey sessions he obtained his discharge.

[3] The Hanserd Knollys Society was founded in London in 1845, "for the publication of the works of early English and other Baptist writers".