Mary's grandmother, Eleanor of Provence, had decided to retire to Amesbury Priory in Wiltshire, a daughter house of Fontevrault.

[6] Mary's parents granted her £100 per year for life (approximately £124,000 in 2025);[3][7] she also received double the usual allowance for clothing and a special entitlement to wine from the stores,[8] and lived in comfort in private quarters.

Probably to prevent his daughter falling into French hands in the event of war with England, Edward refused, and Mary remained at Amesbury, while her allowance was doubled to £200 per year.

She visited her brother Edward in 1293, and regularly attended court, spending five weeks there in 1297, in the run-up to her sister Elizabeth's departure to Holland.

[11] The papal decretal Periculoso was read at Amesbury in 1303, requiring nuns to remain within their religious establishments, but Mary's travels do not appear to have been affected.

[8] It was effectively as a princess, not a nun, that Mary received the homage of the English Dominican friar Nicholas Trevet, a prolific and versatile university scholar and author, who in 1328–1334 dedicated to her his Cronicles,[14] which she may even have commissioned him to write.

And in so moche as hit ys trewly sayde of her and notably this worthy text of holy scripture: optimam partem elegit ipsi Maria, que non auferetur ab ea.

If John's claim was valid, his marriage to Mary's niece would have been rendered null and void, but despite papal mandates for inquests to be made into the matter, the truth was never established.