From 1581 to 1587, he served the English mission, and in the last named year, went to Paris and became Licentiate in civil and canon law.
In 1590, he was entrusted by Father Robert Persons with the government of a small school for English in Eu, Normandy, and remained there until it was broken up by civil war, in 1593.
[3] Besides the usual faculties, Pope Paul V granted to Harrison "Facultates pro archipresbytero Angliæ, in regnis Angliæ, Scotiæ, Hiberniæ, Monæ, et aliis locis dominii regis Magnæ Britanniæ, ac pro personis eorundum regnorum et dominiorum tantum" on 23 July 1615.
[5] In 1621 he sanctioned a protest sent to Rome by ten representatives of the secular regarding the institute established by Mary Ward as being opposed to the decrees of the Council of Trent.
To this end he aided Dr Matthew Kellison, president of the English College, Douai, in lessening the influence of the Jesuits there.