Although often overshadowed in modern historiography by her better-known parents, she is now known to have played an important part in her family's struggles against Llywelyn ap Gruffudd and to have helped to secure the frontline at Shropshire in the run-up to English conquest of Wales.
In due course John the younger would succeed to the baronies of Clun and Oswestry, but as long as the dowager countess of Arundel remained alive the FitzAlans did not possess the complete earldom or its title.
The couple's son Richard FitzAlan was a boy of about five at the time of his father's death and was committed to the wardship of his maternal grandfather, Roger Mortimer of Wigmore.
[2] Serious errors in our nineteenth-century sources have led to the enduring misconception that Isabella Mortimer married Ralph d' Ardern soon after the death of John FitzAlan and had three husbands in all.
[3] In late 1282, as a second war with Llywelyn ap Gruffudd got under way, Isabella was replaced by her younger brother Edmund in most of her custodial interests, including the frontier fortresses.