In 1599 he was appointed to the command of 150 foot, and was actively engaged during the rebellion of Hugh O'Neill; and it appears from a letter of his to Lord Shrewsbury that he even endeavoured to procure the assassination or banishment of O'Neill but in this he was unsuccessful.
The collection appeared with a dedication to Gilbert Talbot.
Gilbert and Sullivan | W. S. Gilbert | Humphrey Gilbert | Gilbert | Gilbert O'Sullivan | Gilbert Gottfried | Gilbert Burnet | George Gilbert Scott | Gilbert Islands | Gilbert du Motier, marquis de Lafayette | Gilbert, Arizona | Cass Gilbert | Paul Gilbert | Giles Gilbert Scott | Gilbert Stuart | Gilbert de Clare | Port Talbot | Brantley Gilbert | John Talbot, 1st Earl of Shrewsbury | Hurricane Gilbert | Gilbert du Motier, Marquis de Lafayette | Gilbert Arenas | Stephen Talbot | L. Wolfe Gilbert | Gilbert White | Gilbert Elliot-Murray-Kynynmound, 1st Earl of Minto | Gilbert Bécaud | Chad Gilbert | Talbot | Philippe Gilbert |
She is sometimes confused with another Portuguese lady, Beatrice, wife of Gilbert Talbot, 5th Baron Talbot and subsequently of his steward, Thomas Fettiplace of East Shefford in Berkshire.
He left another son known as Rhys Mechyll(d.1244), who had a son named Rhys Fychan ap Rhys Mechyll and a daughter named Gwenllian Mechyll, who eventually became his heiress and married Gilbert Talbot(d.1274), grandfather of Gilbert Talbot, 1st Baron Talbot(d.1345/6).
In 1596, Segar accompanied the Earl of Shrewsbury to invest Henry IV of France with the Order of the Garter, witnessing Henry's famed Royal entry into Rouen.