Interior
Good largely mid-C19 interior. Nave roof in 4 bays with short extra section on east has arch-braced tie beam trusses on carved stone corbels with blank shields and pendants; quatrefoils to spandrels and wall-plate with further carved tracery detail between tie beams and principal rafters. 2-bay chancel roof similar but with angels to corbels and similar roofs again to transepts but without the tie beams; plain panelled roof to crossing, which has 2-centred arches on east and west, entirely C19 save for some medieval work at the bases of the responds to the eastern arch. Organ gallery (the neo-Norman cased organ was originally made for the chapel at Penrhyn Castle) with tiered benches at west end of nave has balustrade of intersecting trefoil-headed tracery with quatrefoils supported on 3 wide arches, central 4-centred, outer segmental. C19 benches with traceried ends in nave and plain trefoil-headed tracery screens to transepts; late C20 slate pulpit in stripped-down Gothic style; small octagonal pedestal font with canopied and crocketed cover (1909) commemorating Emma J.S. Douglas-Pennant; late C19 Gothic reading desk and chair. Nave has polished stone slab floor continued through crossing, beyond eastern arch of which are 3 steps to the sanctuary, lower of which is stone but the other 2 and the sanctuary floor itself of slate slabs; scrolled ironwork altar rails in memory of Owen Maelgwyn Roberts, killed in World War II, and large late C19 orange-red marble reredos obscuring lower part of east window; this has stained glass depicting the Last Judgement commemorating Edmund Gordon Douglas-Pennant, given by his widow, Maria in 1887; stained glass in nave south-eastern window showing SS. Tegai, David and Deiniol commemorates Revd. R.W. Griffith (d.1890) and there is further C19 stained glass in south window of south transept.
Monuments: below the gallery in the south-west corner of the nave (formerly on south side of chancel) is fine C15 tomb-chest, only 2 sides of which are now visible owing to its corner position, traditionally thought to be that of either the first or second Sir William Griffith of Penrhyn and his wife: side has 6 panels with cusped and crocketed ogee canopies divided by crocketed pilasters, each containing an angel dressed in a surplice and holding a blank shield, end of 3 panels; recumbent effigies on top, man in armour, his head resting on a mutilated helm, his feet on a crouching lion, woman in long sideless gown over tight-fitting undergarment, her head on a double cushion supported by an angel. On south wall of chancel is marble memorial to John Williams, Archbishop of York (d.1650), who had acquired the Penrhyn Estate in 1622: round-arched recess with panelled soffit and decorated spandrels flanked by bracketed Corinthian columns with entablature and segmental pediment broken by his coat-of-arms and archbishop's mitre; recess contains gowned and capped figure of Williams, kneeling at a prayer desk holding a scroll in his left hand; long Latin inscription beneath but his helm and spurs which once hung nearby are now gone. On north wall is a restrained neo-Romanesque slate wall tablet to George Hay Dawkins-Pennant (d.1840), builder of Penrhyn Castle, who was buried at Chipping Norton (Oxon.) and a triangular wall monument to his eldest daughter and heiress, who died at Pisa in 1842. Pride of place must, however, go to the superb monument by Richard Westmacott, erected in 1821 to Richard Pennant (d.1808) at the instigation of his widow, Anne, who had died in 1816: of white marble it consists of a pedimented sarcophagus, flanked by heroic and classically-costumed figures of a quarryman leaning on a staff and a peasant girl with her distaff, both contemplating a frieze of 4 groups of putti symbolising the state of the district before Pennant's succession to the Penrhyn Estate and his improvements in slate quarrying, education and agriculture; a long inscription below further eulogises his achievements. Memorials to the fallen of First and Second World Wars on nave north and south walls respectively.