In the century before the Lordship was founded, Brycheiniog had been contested between its traditional dynasty, and that of Ferlix (a realm at the heart of Rhwng Gwy a Hafren).

The Book of Baglan reports that Bleddyn ap Maenyrch, heir of the traditional dynasty of Ferlix (who had by now lost Ferlix itself, to Elystan Glodrydd's heirs), was the King of Brycheiniog during the time of the Norman invasion of England (possibly by acquiring a claim through his mother, the niece of Tewdwr ap Griffri).

After suppressing the Saxon part of Eadric's revolt, William FitzOsbern, 1st Earl of Hereford went on to defeat three prominent southern Welsh princes who had supported Eadric, including Rhys ap Tewdwr (son of Tewdwr ap Cadell), the powerful king of Deheubarth.

Emboldened by this, Bernard launched attacks on an area under Rhys' influence - Brycheiniog - while the sons of Bleddyn ap Cynfyn, Gruffydd's half-brother, attacked Deheubarth; this was likely a co-ordinated action between Bernard and Bleddyn ap Cynfyn's sons.

Rhys later re-established his position with Irish assistance, and in April 1093 he and Bleddyn attacked Bernard while he was building a castle at Brecon.

The Welsh Annales clearly state that Rhys was killed 'by the French who were inhabiting Brycheiniog' (implying that Bernard had already taken over the kingdom).

However, Bernard's wife, Nesta, dramatically swore an oath, in the presence of King Henry I, that Mahel was a bastard.

By the following year - 1136 - a number of Welsh princes and magnates had begun to see this as an opportunity to recover lands they had lost to Marcher lords,[4][5] and broke out in revolt.

Gwenllian's attempted defence nevertheless inspired further opposition to the Marcher Lords, ultimately leaving her son, Rhys ap Gruffydd as a much more powerful ruler than his parents had been.

Sibyl's sister-in-law was married to Richard Fitz Pons, a powerful supporter of Bernard, who owned lands in Herefordshire close to the border of Brycheiniog (as well as elsewhere) - the Barony of Clifford.

However, Roger, who was childless, detached the region around Bronllys, the whole of the Cantref Selyf, and gave it as an independent Lordship to his cousin, Walter Fitz-Richard, the son of Richard Fitz-Pons.

When King John's son, Henry III, acceded to the throne, he was keen to make peace with the barons after the problems his father had encountered.

Subsequently, Humphrey and Gilbert settled their differences and persuaded the king to commute the decision in return for large sums of cash.

When she died, in 1311, without immediate heirs, King Edward transferred the Bronllys Lordship to Rhys ap Hywel as well.

Roger Mortimer, now in effective control of the country (ostensibly on behalf of Edward's son, but in reality for his own benefit), restored the status quo ante as best he could; Rhys ap Hywel was restored to his portion of the Lordship of Brecknock, while Humphrey's son, John de Bohun received the rest.

However, King Edward III, after taking control of government from Roger Mortimer (whom he had executed for treason), allowed himself to be persuaded that a place like the Lordship of Brecknock should be ruled by a powerful magnate (like Humphrey) not a weak one (like Philip).

Nevertheless, Anne of Gloucester, daughter of Mary de Bohun's elder sister Eleanor, petitioned Henry for her grandfathers lands - which should rightly be hers - to be returned to her.