Richard’s fleet had scarcely left the Irish coast when the hollow nature of the submissions was displayed. An act of treachery caused another rising when the English endeavoured to capture Mac Murrough while their own guest at a banquet; an attempt from which he escaped by the ingenious warning of his bard.

The O’Tooles defeated the English near Dublin ; while Art himself surpassed his capture of New Ross by taking the strong town and castle of Carlow (1397). This was the greatest advance he had yet made, for it gave him the control of all the fords of the Barrow, broke in two the English line in Leinster, and brought Mac Murrough into touch with the O’Moores of Laoighis.

His forces now freely roamed as far west as the River Nore and beyond it. Meanwhile the midland clans were also active, and Calvagh O’Connor, the heroic son of the chief of Ul Failghe, defeated the English, and took the Earl of Kildare prisoner (1398).
The Irish were now to strike a blow which proved, indirectly, to be the most disastrous that they had ever dealt to Sir John Davits.
 
England. Richard had left as his viceroy the young Roger Mortimer, Earl of March, who was the recognised heir to the throne of England. In this prince was united some of the most famous blood of both England and Ireland, including that of the Mac Murroughs themselves.

 Descended from the Mortimer who was Viceroy at the time of the Bruce Invasion  he traced his ancestry on one side to Hugh De Lacy, and on the other to Eva Mac Murrough and Strongbow. His mother was the daughter of Lionel, Duke of Clarence, and through her he was not only heir apparent to the English Crown, but also heir to the remote titles of De Burgh and De Courcey.

The Earl gathered an army to meet his distant kinsman Art Mac Murrough ” Caomhanach.” The latter now controlled not only all South Leinster, but also the south of Osraidhe, and it was in the latter territory, away beyond the Nore, that the two armies met at Kelts. The English were defeated, and the Earl of March was slain (1398).

The loss of Richard’s accepted heir in this battle was a chief cause of the ” Wars of the Roses,” which for thirty years made all England a battlefield.