He had in the late reign been suspected of leaning towards Popery, but had outwardly conformed to the established religion, and had at length been chosen Master of University College.
Soon after the accession of James, Walker determined to throw off the disguise which he had hitherto worn.

He absented himself from the public worship of the Church of England, and, with some fellows and undergraduates whom he had perverted, heard mass daily in his own apartments.

One of the first acts performed by the new Solicitor General was to draw up an instrument which authorised Walker and his proselytes to hold their benefices, notwithstanding their apostasy.

Builders were immediately employed to turn two sets of rooms into an oratory.

In a few weeks the Roman Catholic rites were publicly performed in University College.