Today (July 1st) is the usual day that St Oliver Plunkett's feast is celebrated but this year the Feast of the Sacred Heart is today, so Oliver's feastday was celebrated yeserday. Oliver Plunkett (1625-81) was beheaded at Tyburn on 1 July 1681 mainly because he was not willing to compromise on his faith.
[This Drogheda website offers plenty of information on St Oliver]
[This blog of Fr John Hogan of the Fraternity of St Genesius offers a broader context in his reflections on the Irish Martyrs]
The reliquary still at the Siena Convent that contained his head until 1921 bears the Plunkett arms on the silver plate of the door.
A stained glass window at St Peter's Church, West Street, Drogheda also bears the arms and image of Oliver
The arms are also on the choir balcony at St Peter's along with those of Corker, Sheldon and Cotton.