In 1330 Edward III. granted to Roger Mortimer, Earl of March, the moiety of Meath and the privileges exercised in Trim Castle. He was hanged as a traitor the same year, but Trim was restored to his widow.
Roger, Earl of March, was killed by the Irish in 1398, and the next year Richard II. landed at Waterford to avenge his cousin’s death, with Humphrey, son of the Duke of Gloucester and Henry (afterwards Henry V.), son of the Duke of Lancaster. The boys he brought with him as hostages, and upon returning to England he left them as prisoners in Trim Castle. A very small steel spur, inlaid with silver, was found in the castle yard in 1836, which may have belonged to one of the princes.
In 1400 Henry IV. appointed a custodian to the late Earl of March’s records at Trim and elsewhere. At this time the castle was in his hands owing to the minority of the heir.
The Privy Council in England (1403) notified to the King that the castle was in a most dilapidated condition.
From this time forward Parliaments were continually held at Trim, while in 1418 the Earl of Kildare, Sir Christopher Preston, and John Bedlow were imprisoned in the castle.
Four years later Richard Talbot, Archbishop of Dublin, resided in the fortress, and in 1425 Edmund, Earl of March, died there while Lord Deputy.
But, perhaps, the most palmy days of Trim Castle were in 1449, when Richard, Duke of York, came to Ireland as Lord Lieutenant, and held his court there.
The mint was opened in 1460, and the following year Christopher Fox was appointed Comptroller.
A Parliament held at Trim in 1465 enacted that any one discovered robbing might be killed, and in Meath their heads were to be sent to the Portreffe of the town of Trim, to be put on the castle wall. Several skulls have been found in the moat.
In 1495 an Act of Parliament passed at Drogheda provided that only Englishmen should be constables of Trim and the other principal castles.
The liberty and lordship of Trim were at this time annexed to the Crown for ever.
In 1541 an order was issued to restore the castle, half the cost of which was to be paid by the country.
A grant was made to Sir James Carroll, Lord Mayor of Dublin, in 1610, to build upon the ruins of the castle a house for the King, and also a jail within the castle enclosure.