After Augustinian Friar William Tirry was arrested at Fethard while vested for Mass on Holy Saturday, 25 March, 1654, he was tried at Clonmel on 26 April, by a jury and a panel of Commonwealth judges, including Colonel Richards, for violating the Proclamation of 6 January 1653, which defined it as high treason for priests to remain in Ireland.
In September 1688 he was commissioned by King James II to raise a new regiment of foot to provide him with reliable troops to counter the menace of William's invasion.
In the early phase of the ensuing Williamite war in Ireland, the city of Derry in Ulster, which was held for William by Lieutenant-Colonel Robert Lundy, was menaced by the Irish army of Tyrconnell and James II.
They sailed from Liverpool in 1689 on nine transport ships escorted by the fourth-rate frigate HMS Swallow and reached Lough Foyle downstream of the city on 15 April 1689.
As Lundy's poorly organised troops streamed back towards the city walls, he issued several contradictory orders to Cunningham and Richards.
[7] Richards and Cunningham therefore sailed back to Britain without landing their troops just at the time when the Siege of Derry began in earnest.
As Derry was able to hold out until a second relief force under General Percy Kirke arrived, questions were raised in the English Parliament about Cunningham's and Richards' conduct.
It is sometimes wrongly stated that he was the father of Jacob Richards an engineer officer, who also served William in Ireland (1689–91) where he was wounded during the Siege of Carrickfergus.
William Tirry was beatified by Pope John Paul II along with 16 other Irish Catholic Martyrs on 27 September 1993.