Read this and answer the question. If the question is unanswerable, say "unanswerable".

In England, Presbyterianism was established in secret in 1592. Thomas Cartwright is thought to be the first Presbyterian in England. Cartwright's controversial lectures at Cambridge University condemning the episcopal hierarchy of the Elizabethan Church led to his deprivation of his post by Archbishop John Whitgift and his emigration abroad. Between 1645 and 1648, a series of ordinances of the Long Parliament established Presbyterianism as the polity of the Church of England. Presbyterian government was established in London and Lancashire and in a few other places in England, although Presbyterian hostility to the execution of Charles I and the establishment of the republican Commonwealth of England meant that Parliament never enforced the Presbyterian system in England. The re-establishment of the monarchy in 1660 brought the return of Episcopal church government in England (and in Scotland for a short time); but the Presbyterian church in England continued in Non-Conformity, outside of the established church. In 1719 a major split, the Salter's Hall controversy, occurred; with the majority siding with nontrinitarian views. Thomas Bradbury published several sermons bearing on the controversy, and in 1719, "An answer to the reproaches cast on the dissenting ministers who subscribed their belief of the Eternal Trinity.". By the 18th century many English Presbyterian congregations had become Unitarian in doctrine.

Which religion was established in secret in 1660?
unanswerable