Ralph Weldon asserts that Jones was removed from Wales to England when scarcely a year old (Chronicle of the Benedictine Monke, p. 100).
'His mind being much inclined to the Roman religion,' he quit the university, and within a few days of his arrival in London his parents died of the plague.
Thereupon Jones left England for Spain, was received into the English Collage at Valladolid, then under the direction of the jesuits, 20 December 1596, and took the college oath on the feast of St. Alban, 1597.
In October 1599 he was admitted into the Benedictine abbey of St. Martin at Compostella, and became a monk of that order, taking, in religion, the name of Leander à Sancto Martino.
Although ordered to the English mission, Jones acted successively as novice-master at the abbey of St. Remigiua at Rhelms, and at St. Gregory's at Douay.
When in 1619 the present English Benedictine congregation was formally approved by Pope Paul V, Jones was elected its first president-general for the usual triennial period, and wua re-elected in 1633.
When early in 1634 Urban VIII determined to send an accredited agent to England to open diplomatic relations towards obtaining religious toleration for Catholics in the British Isles he chose Jones for the important mission.
Wood describes him as 'the ornament of the English Benedictines in his time,' adding that 'he was a person of extraordinary eloquence generally knowing in all arts and sciences, beloved of all that knew him and his worth, and hated by none but by the puritans and jesuits (Athenæ Oxon.