His father's sister Mary was mother by her second husband of Thomas Ravis, later bishop of London, at whose request L'Isle composed an epigram against Andrew Melvill.
[2][3] He resigned his fellowship after 1608 in order to take possession of an estate which had been left him in the ancestral home at Wilbraham, Cambridgeshire.
He took part in a violent quarrel in King's College in August 1608, which resulted in the wounding of the vice-chancellor Roger Goad.
Goad brought the matter to the notice of the chancellor, Robert Cecil, 1st Earl of Salisbury; L'Isle then wrote submitting to Salisbury's jurisdiction and begging not to be deprived for his offence, citing thirty years' study in the university, and no action was apparently taken against him.
Like his younger brother Edmund, who died a month later, he was buried at Walmer, where a monument to their memory was erected in the church.
[5] Interest in the doctrinal position of the early English church on various points in controversy in his day first led him in that direction.
The book concludes with the Lord's Prayer, the Creed, and Ten Commandments in Anglo-Saxon, with a verbal interlinear translation intended to serve as exercises for beginners.
The major editions of Anglo-Saxon works which he had projected were Ælfric's translations of the Pentateuch, and the books of Joshua, Judges, and Job, and also the Saxon-English Psalter.
In 1619 he wrote two Latin hexameter poems addressed to his neighbour, Michael Dalton, and prefixed to the second edition of his Countrey Justice published in that year.