Like St. John Kemble and St. John Wall on August 22, St. David Lewis was a victim of the Popish Plot.
The particularly repellent aspects of the Popish Plot are
1) There was no plot at all: Titus Oates perjured himself and made it all up
2) Parliament's leaders, like Lord Shaftesbury, Anthony-Ashley Cooper, fomented it
3) Charles II knew it was not true and yet seemed powerless to prevent it
4) The vaunted English Court system was duped by it and was an accessory to multiple injustices--like that experienced by today's saint!
It took the Courts far too long to recognize this injustice--at which time it started finding the accused not guilty--and Parliament never truly admitted its culpability. Titus Oates was found guilty of perjury but was soon rewarded by the regime of William and Mary with a pension. Charles II protected his brother and his wife, although James and Mary Beatrice fled to Ireland in exile. Charles did not give in to the desire of Parliament to bypass his Catholic brother the succession, either.
St. David Lewis was born and raised in a Protestant family but when he went to Paris at age 16 he was moved to become a Catholic! He was ordained in 1642 in Rome and joined the Jesuit order in 1645--like St. John Kemble he served in Monmouthshire for some years.
In November of 1678, he was arrested, taken to London and questioned in connection with the Popish Plot. Lord Shaftesbury offered him freedom if he gave information about the Plot and renounced his Catholicism. David said he had no knowledge of the Plot and would not renounce his faith.
St. David Lewis was then returned to Monmouthshire and executed in Usk on August 27, 1679. He is the last Welsh marytr. Like Blessed Dominic Barberi, his memorial is on August 26 to avoid conflict with that of St. Monica, St. Augustine's mother. This blog contains some great detail about the Last Welsh Martyr!